Yashavant Kanetkar [email protected] Solutions Using J2EE / Lecture 01 1 Yashavant...

Enterprise Solutions Using J2EE / Lecture 01 1

Yashavant [email protected]

Objectives

Current software scenarioWhy should we use JavaDifferent Java TechnologiesJava based software development

Software Scenario

Software

Desktop

Web

Embedded

DistributedOS

Compiler

Dev. Dri.

C/ C++

Java / VB / C# / VC++


Why Java?Easy to develop

Check as you type - Like Spellcheck, GrammarcheckIntellisense - Function parametersVery good examples / samplesExhaustive documentation – http://java.sun.com/docs/

Rapid Application Development (RAD)Media playerEmbedded Web browserEmbedded Excel browser

Same language, same tool for multiple applicationsEasy to manage large projects (1,00,000 lines code)

Source controlDebuggingProject organization

Java Technologies

J2SE J2ME J2EE

Connectivity - Virus SignaturesPluggable interface - Google toolbarFunctionally rich programs

HelpSearchUpdate

J2SE Track

Desktop


Smaller screensDifferent user-interfacesIntermittent connectivitySynchronization ( address book )

J2ME Track

Embedded

J2EE TrackPortalsThemesModules

Internet

Java Based Software Development

• RAD tool• Wizard generated skeleton code• Debugging help• Industry standard• www.netbeans.org

Java IDEJava Development Kit – Compiler, Linker, etc.Java Runtime Environment

VJ++JBuilderVisual CaféNetBeans

Choices

java.sun.com – JDK 6.0 c:\Program Files\Java\jdk1.6.0


Constants, Variables, Keywords

Yashavant Kanetkar

[email protected]

ObjectivesLearning stepsConstants and VariablesTypes of constants and VariablesHow to identify typesRules for creating variablesKeywords

In The Beginning...

Alphabets, Digits Alphabets, Digits, Sp. Symbols


Statements or Instructions

Program

English Java

Paragraph

Sentences

Words, Numbers


AlphabetsA - Z, a - z

Sp. SymbolsTotal - 32

Alphabets, Digits, Sp. Symbols

Digits0 - 9

Constants & Variables

3 x + 2 y

x = 3y = 5x = 7z = 3.14w = 'A'

Variables Constants

3, 5, 7 - Integer constants3.14 - Real constant'A' - Character constantw, x, y, z - Variables

ConstantsLiterals

VariablesIdentifiers

Integer Constants

4. Valid Range: -2147483648 to +2147483647

Rules:Ex. 421 -62 +45 4096

1. No decimal point

2. May be +ve or -ve. Default: +ve

32,500 4 7 33. No comma or spaces

72 72.0


Real Constants

1. Must contain a decimal point2. May be +ve or -ve. Default: +ve3. No comma or spaces4. Valid Range: -3.4x 1038 to +3.4 x 10385. Different forms:

Rules:Ex. 427.62 +24.297 -0.00254

427.62+24.295-0.00254

4.2762E22.4295e1-2.54e-3

ExponentMantissa4.2762 2E

Exponential FormFractional Form

Rule : A single character enclosedwithin a pair of ’ ’.

Character Constants

‘Z’’Nagpur’

Ex. ’A’ ’m’ ’3’ ’+’

Are They OK?

Java Data Types ‐ Primitives

charData Type Range Size

byteshortintlong

floatdouble

0 to 65535-128 to +127-32768 to +32767-2147483648 to +2147483647

-9223372036854775808 to +9223372036854775807 -3.4e38 to +3.4e38-1.7e308 to +1.7e308

21248

48

boolean 1-bittrue / false

Fixed but not fixedType determines behaviour not size


Is it necessary to identify types?Yes.

Variables

How many types?As many as the types of constants.

Why?

y = 4y = ’A’Why?

MemoryWhat Happens in Memory...

xy

z

x = 3

3y = 4z = x + yprint z

VariableAn entity whose value can changeA name given to a location in memory

x = 5

54

7

Would this work?int xyz int abc123int 123abc

33.0’3’abc

How to Identify TypesInteger ConstantReal ConstantCharacter Constant

?

??

int aa = 3 b = 3.0 c = ’3’

float b char c

int, float, char - data types / primitivesa, b, c - variables3, 3.0, '3' - constants / literals


Cannot begin with a digit

Rest can be alphabets, digits, underscores or $

Ex. pop98 si_int

Rules for Building Var. Names

Any Length

No commas or spaces

Variable names are case sensitive

Ex. abc ABC Abc aBc AbC

_- si-int

si_int

All are different

Java KeywordsHow many?

And How About This...

int float float charfloat = 3 char = 3.14

integer areal bcharacter c

Would This Work?

48

Words whose meaning already stands explainedWhat are Reserved words? Same as keywords

Any examples? int, float, charWhat are Keywords?

1Enterprise Solutions Using J2EE / Lecture 03

First Java ProgramYashavant [email protected]

ObjectivesFirst Java programPrinting valuesGeneral form of println( )Function, Class and PackageType of comments

Where Do We Stand?




Program


The First Java Program

p = 1000.50fn = 3 r = 15.5fsi = p * n * r / 100

float p, r, siint n

TipsAll variables must be declared+ - * / are Arithmetic Operators

2 \ 3232 3÷

Printing Values...float p, r, siint n p = 1000.50fn = 3 r = 15.5fsi = p * n * r / 100 System.out.println ( si )

p1000.50 3 15.50

n r

465.25

si

( ) Parentheses Braces[ ] Brackets

Class Object Function

Statement Terminators

float p, r, si ;int n ;

: colon ; semicolon

I am a boy I go to school

float p, r, siint n

Statement Terminator

float p, r, si ;int n ;

float p, r, si ; int n ;


What To Execute

float p, r, si ;int n ;p = 1000.50f ; n = 3 ; r = 15. 5f ;si = p * n * r / 100 ;System.out.println ( si ) ;

public static void main( )

ScopeDelimiters

Function

class SimpleInterest

package simpleinterest ;

Keyword

Keyword

Tips…A Java program is a collection of one or more packagesEach package can contain multiple classesEach class may contain multiple functionsEvery variable should belong to a function Every function must belong to a classEvery class must belong to a packagepackage, class, public, static, void – Keywordspublic static is same as static publicJava is case-sensitive and free-form language

package simpleinterest ;class Simpleinterest


float p, r, si ;int n ;p = 1000.50f ; n = 3 ; r = 15. 5f ;si = p * n * r / 100 ;System.out.println ( si ) ;

Comments Are Useful/* Calculation of simple interest */

NoteRemark


Types Of CommentsSingle line comments

Documentation comments

Multi-line comments

/* Cal. of simple interestAuthor – Yashavant KanetkarDate – 25 Jun 2008 */

si = p * n * r / 100 ;// calculation of simple interest

si = p * n * r / 100 ; // calculation of simple int.

/*** @param args the command line arguments*/

Tips About CommentsAny number of comments anywhere

Nested comments -/* .............. /* ....... */ ........ */

si = p * n * r / 100 ;/* formula */ /* formula */


Using NetBeans


Objectives

Understanding NetBeans IDECreating a program using NetBeansWhat is Java PlatformJava FAQs

NetBeans IDE

I D ECompiler

InterpreterLinker

Editor typing / editing

Java to Bytecode

Debugger

Bytecode to m/c


Steps In Using NetBeans

Create a Project Add Code to the Generated Source File Compile the Source File Run the Program

Create New Project

Select Project Type


Project Name & Location

packagename.classname

Wizard Generated Code

Package pkg

class One class Two

fun1

fun2

fun3

fun4

Realign

Add New Code

float p, r, si ;int n ;p = 1000.50f ; n = 3 ; r = 15. 5f ;si = p * n * r / 100 ;System.out.printf ( "%f", si ) ;


Build & TestBuild | Build SimpleInterest Project F11

Run | Run SimpleInterest Project F6

What Happens

SimpleInterest.java SimpleInterest.classSimpleInterest

What Is Run Anywhere

SimpleInterest.java


What Is Java Platform

Hardware

Windows / Mac / Unix

Java Virtual Machine

Java API

SimpleInterest.java

Java Platform

API = Library of classes in form of packages


Generic Programs


Objectives

More general programs

Modulus operator

Command-line arguments

package sample ;import java.io.* ;import java.lang.* ;public class Sample

public static void main ( String[ ] args ) throws Exception

float p ; String str ;BufferedReader b ;b = new BufferedReader ( new InputStreamReader (

System.in ) ) ;str = b.readLine( ) ;p = Float.parseFloat ( str ) ;System.out.printf ( "%f", p ) ;

Receiving Floats


package simpleint ;import java.io.* ;import java.lang.* ;public class SimpleInt


float p, r, si ; int n ;BufferedReader b = new BufferedReader (

new InputStreamReader ( System.in ) ) ;String str ; System.out.println ( "Enter values" ) ;str = b.readLine( ) ;p = Float.parseFloat ( str ) ;

Generic Program

str = b.readLine( ) ;n = Integer.parseInt ( str ) ;str = b.readLine( ) ;r = Float.parseFloat ( str ) ;si = p * n * r / 100 ;System.out.println ( "Simple int. = Rs. " + si ) ;

How To Supply Values


Interchange Contents of 2 Variables

public static void main( ) throws Exception c d

5 10tx

c d5 10

t5

c d10 10

t5

c d10 5

t5

t = c ;c = d ;d = t ;System.out.println ( c + " " + d )

int c, d, t ;

// receive values in c and d

5 10

10 5

One More Way

c d25 10c d

25 15c d

10 15c = c + d ;d = c - d ;c = c - d ;

c d15 10

public static void main( ) throws Exception

int c, d ;

UtilityRoll nos. in Asc/Desc. orderNames in alphabetical orderDates in chronological order

// receive values in c and d

15 10

System.out.println ( c + " " + d ) ;

10 15

2 6 9 1 3


int n ;// receive value of n

Sum of Digits

26913

d1 d3d2 d4 d5

.. ..

.. .. 26913 / 10

26913 % 10- Division2691- Modular div.3

Mod

26910

3

10 26913 2691


Utility

The Whole Picture


…3 2691d5

n

d4

d3

d2

d1

1

9

6

2

269

26

2

26913

d5 = n % 10 ;

d4 = n % 10 ;

d3 = n % 10 ;

d2 = n % 10 ; d1 = n % 10 ; s = d1 + d2 + d3 + d4 + d5 ;System.out.println ( s ) ;

n = n / 10 ;

n = n / 10 ;

n = n / 10 ;

n = n / 10 ;

21

Leap year or notOdd / EvenPrime or not

System.out.println ( args[ 0 ] ) ; System.out.println ( args[ 1 ] ) ; System.out.println ( args[ 2 ] ) ;

Command Line Arguments

package myargs ;class Myargs

public static void main ( String args[ ] )

Array of String objects

Supplying Command Line Arguments


Java InstructionsYashavant Kanetkar

[email protected]

Types of Java InstructionsType declaration instructionExpression instructionNuances of boolean, char, int, etc.Mixed mode expressions

Objectives

Type DeclarationExpressionControlSynchronizationGuarding

Where Are We....




Program


Type Declaration InstructionEx. int i, j, k ;

float a, b, c ;char ch ;

int i ;i = 5 ;

int i = 5 ;

int a = 5, b = 10, c = a + b * 5 % 2 ;

int a, b, c, d ;a = b = c = d = 5 ;

int a = b = c = d = 5 ;

order isimportant

Expression InstructionEx. s = d1 + d2 + d3 ;

si = p * n * r / 100 ;+ - * / %

For exponentiation -

double a ;a = Math.pow ( 2, 5 ) ;

Arithmetic Operators

a = b ( c + d ) ; a = b * ( c + d ) ;

i = j * k + 3 ;j * k + 3 = i ;

i = 3 ;3 = i ;

a = 2 ** 5 ;a = 2 ^ 5 ;

boolean a = false ;System.out.println ( "a = " + a ) ;System.out.println ( "Result = " + ( 4 > 3 ) ) ;

Boolean Type

a = false

Result = true

Do not use true / false as variable names

true is not 1 and false is not 0

int a ;a = 3 < 4 ;

boolean b ;b = 3 < 4 ;

Boolean can take a value true or false

Result of a Boolean expression is true / false


Char Typechar ch = ’A’ ; System.out.print ( ch ) ; - 65 is not stored

- Unicode is stored- Size – 2 bytes

char ch = ’A’ ; char dh = ch + 1 ;System.out.print ( dh ) ;

char is promoted to intbefore arithmeticSolution:

int dh = ch + 1 ;

Integer Type4 types – byte, short, int, longMost common – intbyte and short are used to save spacelong is used to deal with very big integer valuesBy default number without a decimal point is intDuring assignment value being assigned should notexceed the range of the variable

byte a = 300 ;short b = 40000 ;int c = 2200000000 ;

Real Type2 types – float, doubleMost common – floatdouble is used to deal with very big real valuesBy default number with a decimal point is doubleDuring assignment value being assigned should notexceed the range of the variable


float a = 3.14 ;

int b = 3.14 ;

Mixing Types

int a = ( int ) 3.14f ;Typecasting

float a = 3.14f ;float a = 3.14F ;

short a = ( short ) 32768 ;System.out.println ( a ) ; -32768

Widening conversions take place automaticallylong l = 40000 * 2 ;Narrowing conversions report errorsshort s = 40000 ;

Possible loss of precision is reported as errorshort s ; short s ; int i = 5 ;s = 2 * 5 ; s = 2 * i ;



Precedence & Associativity

What is mixed mode arithmetic?What is precedence of operators?What is associativity of operators?Printing functions and their features

Objectives

Mixed Mode Arithmetic

5 / 2 5.0f / 2 5 / 2.0f 5.0f / 2.0f 2 / 5 2.0f / 5 2 / 5.0f 2.0 / 5.0f

22.52.52.500.40.40.4


Operand1 Operand2 Result

int intfloat floatint float float int

All Possible Cases

intfloatfloatfloat

Which Is Correct?

float c, f = 212.0f ;

c = 5 / 9 * ( f - 32 ) ;

c = 5 / 9.0f * ( f - 32 ) ;

c = ( f - 32 ) * 5 / 9 ;

Note: Parenthesis matter

0.0

100.0

100.0

Hierarchy/Priority/Precedence

c = a + b * c % 5 - d * 61

Operators

* / %+ -=2

4

6

3

5


Associativity - I

c = 3 / 2 * 5 ; / * L to R AssociativityLeft - Unambiguous1

23

Right OperandOperator RemarkLeft Operand

L ok, R Not ok3/ 52 or 2 * 5 L Not ok, R ok2 or 3 / 2*

Right OperandOperator RemarkLeft Operand

Associativity - II

a = b = 5 ;

L ok, R Not okb or b = 5a1st =L Not ok, R ok5a or a = b2nd =

12

= R to L AssociativityRight - Unambiguous

Try: a = 2 * 3 / 4 % 5

Output Functions

println( ), print( ), printf( ) – Outputprintln( ) – print and go to new lineprint( ) – print printf( ) – for formatted printing

System.out.print ( "First " ) ; System.out.print ( "Second " ) ; System.out.println ( "Third " ) ; System.out.println ( "Fourth" ) ;

First Second ThirdFourth


printf( )

General FormS.o.printf ( "format string", list of variables ) ;

S.o.printf ( "Enter values of c and d" ) ;List of variables is optional

S.o.printf ( "%i %i %i", a, 35, 2 + 6 % 3 ) ;List can contain var., const., or expressions

printf( )

S.o.printf ( "format string", list of variables ) ;

System.out.printf ( "\nSimple Interest = Rs. %f", si );

can contain

Format specifiers- int - %d- float - %f- char - %c

Escape sequences

Any othercharacters


Decision Control Instructions - I


ObjectivesWhat are Control Instructions What are decision control instructionif, else keywordRelational operators

InstructionsType Declaration InstructionsExpression InstructionsControl Instructions Synchronization InstructionsGuarding Instructions


Control InstructionsWhat are they?- Control the sequence of execution of instructions

What different types?- Sequence- Decision- Repetition- Case

Normal Java Programclass sample


int .... ; float .... ;// receive inputa = .... ;b = .... ;System.out.printf ( .... ) ;

Tip: Sequence CI is the default CI

Decision Control Instruction// Calculation of total expensesclass totalexpenses


int qty ; float price ;BufferedReader b ;b = new BufferedReader (

new InputStreamReader ( System.in ) ) ;String str ;System.out.println ( "Enter quantity and price" ) ; str = b.readLine( ) ;qty = Integer.parseInt ( str ) ;str = b.readLine( ) ;price = Float.parseFloat ( str ) ;...


// Calculation of total expenses public static void main( ) throws Exception

int qty ; float price ;

// receive qty and price

if ( qty >= 1000 )dis = 10 ;

- qty * price * dis / 100 ;totexp = qty * priceSystem.out.println ( "Total exp = Rs ", totexp );

200 15.50int dis ; float totexp ;

elsedis = 0 ;

1200 15.50

Tipsif, else - Keywords

General form:if ( condition )

statement1 ;else

statement2 ;

Condition is built using <, >, <=, >=, = =, !=

a = b

a = = b

Relational Operators

Assignment

Comparison

// receive qty and price

// Calculation of Total Expensespublic static void main( ) throws Exception

Tip: else block is optional

if ( qty >= 1000 )dis = 10 ;

int qty ; int dis ;float price ;

totexp = qty * price - qty * price * dis / 100 ;

= 0 float totexp ;

System.out.println ( "Total exp = Rs " + totexp ) ;

200 15.50

1200 15.50

One More Way


if ( bs >= 1500 )da = bs * 95 / 100 ;

hra = bs * 20 / 100 ;ca = bs * 12 / 100 ;else

da = bs * 92 / 100 ;hra = bs * 15 / 100 ;ca = 200 ;

public static void main( ) throws …

// receive bs

// Calculation of gross salary

float bs, hra, ca, da, gs ;

if ( bs >= 1500 )da = bs * 95 / 100 ;hra = bs * 20 / 100 ;ca = bs * 12 / 100 ;

elseda = bs * 92 / 100 ;hra = bs * 15 / 100 ;ca = 200 ;

gs = bs + hra + da + ca ;System.out.println ( "Gross salary = Rs. " + gs ) ;

only this belongs to if block

only this belongs to else block

Tip: Hanging else not allowed

// Calculation of gross salary public static void main( ) throws Exception

float bs, hra, ca, da, gs ;// receive bsif ( bs >= 1500 )

da = … ; hra = ... ; ca = … ;else

da = … ; hra = ... ; ca = … ;gs = bs + da + hra + ca ;System.out.println ( "Gross salary = Rs " + gs ) ;

Correct Program

One More Formif ( condition )

statement1 ;statement2 ;

else

statement3 ;statement4 ;

Tip: - Default scope of if and else is onlythe next statement after them.

- To override the default scope use


Decision Control Instructions - IIYashavant [email protected]

Objectives

Program – Leap year or notProgram – First day of any given yearNuances of Modulus OperatorNuances of Comparison Operator

Leap Year or Notclass LeapYear


System.out.println ( "Enter year" ) ;// receive year

int y ;

…

0

4 1996 4991996

Leap

0

4 2000 5002000

Leap

0

4 1900 4751900

Not Leap


if ( y % 100 == 0 )

if ( y % 400 == 0 )System.out.println ( "Leap" ) ;

elseSystem.out.println ( "Not Leap" ) ;

else

if ( y % 4 == 0 )System.out.println ( "Leap" ) ;

elseSystem.out.println ( "Not Leap" ) ;

Nested if-elsestatements are legal

class LeapYear


int y ;// receive year

First Day of Any Yearclass FirstDay


int y ;System.out.println ( "Enter year" ) ;// receive year. . .

2002

The Logic Behind It

………1/ 1/ 2002

1/ 1/ 1 Monday

15/ 1/ 1 Monday

22/ 1/ 1 Monday

29/ 1/ 1 Monday

?

8/ 1/ 1 Monday

1 /1 / 1 Monday29/ 1 / 1 ?

1/ 1/ 1 to 28/1 / 1

1/ 1/ 1 to 31/ 12/ 2001

28 % 7 0

? ? % 7


class LeapYear


System.out.println ( "Enter year" ) ;// receive year

totaldays = normaldays + leapdays ;firstday = totaldays % 7 ;if ( firstday == 0 )

System.out.println ( "Monday" ) ;.. .... ..

leapdays =( y - 1 ) / 4 - ( y - 1 ) / 100 + ( y - 1 ) / 400 ;

int y ;int firstday, normaldays, leapdays, totaldays ;

normaldays = ( y - 1 ) * 365 ;

1/ 1/ 1 to 28/ 1 / 1

28 % 7

0

1/ 1/ 1 to 31/ 12/ 2001

?

? % 7

Are You Sure?4 % 33 % 4

-3 % 43 % -4

-3 % -4

13-33-3

Tip: Sign of remainder is same as sign of numerator

int a = 5, b = 5, c = 5 ;if ( a == b == c )

printf ( "Hello" ) ;else

printf ( "Hi" ) ;

Error


Logical OperatorsYashavant Kanetkar

[email protected]

Objectives

Nuances of decision control instructionWhat are logical operatorsWhen to use themHierarchy of operators

What Will Be The Outputpackage sample ;class Sample


int a = 5, b = 10 ;if ( a >= 20 ) ;

b = 30 ;System.out.println ( b ) ;

; - Null statementDoesn’t do anything on execution

30

if ( a >= 20 );

b = 30 ;


What Will Be The Output

package sample ;class Sample


int a = 10 ;if ( a = 5 )

System.out.println ( "Hi" ) ;

Error – Boolean expression required

else

if ( per >= 40 )S.o.p ( "Third division" ) ;

elseS.o.p ( "Fail" ) ;

if ( per >= 60 )S.o.p ( "First division" ) ;

else

if ( per >= 50 )S.o.p ( "Second division" ) ;

int m1, m2, m3, m4, m5 ;

class Examination


// receive m1, m2, m3, m4, m5per = ( m1 + m2 + m3 + m4 + m5 ) / 5 ;

int per ;

3 ProblemsMatching if - elseMatching Indentation Level

class Examination


int m1, m2, m3, m4, m5, per ;// receive m1, m2, m3, m4, m5 per = ( m1 + m2 + m3 + m4 + m5 ) / 5 ;if ( per >= 60 )

System.out.println ( "First division" ) ;if ( per >= 50 )

System.out.println ( "Second division" ) ;if ( per >= 40 )

System.out.println ( "Third division" ) ;else

System.out.println ( "Fail" ) ;

Anything Wrong?

?


class Examination


int m1, m2, m3, m4, m5, per ;// receive mq, m2, m3, m4, m5per = ( m1 + m2 + m3 + m4 + m5 ) / 5 ;if ( per >= 60 )

S.o.println ( "First division" ) ;if ( per >= 50 && per < 60 )

S.o.println ( "Second division" ) ;if ( per >= 40 && per < 50 )

S.o.println ( "Third division" ) ;else

S.o.println ( "Fail" ) ;

Still Anything Wrong?

class Examination


int m1, m2, m3, m4, m5, per ;// receive m1, m2, m3, m4, m5per = ( m1 + m2 + m3 + m4 + m5 ) / 5 ;if ( per >= 60 )

S.o.println ( "First division" ) ;if ( per >= 50 && per < 60 )

S.o.println ( "Second division" ) ;if ( per >= 40 && per < 50 )

S.o.println ( "Third division" ) ;if ( per < 40 )

S.o.println ( "Fail" ) ;

Is This Better?

class Examination


int m1, m2, m3, m4, m5, per ;// receive m1, m2, m3, m4, m5per = ( m1 + m2 + m3 + m4 + m5 ) / 5 ;if ( per >= 60 )

S.o.p ( "First division" ) ;else if ( per >= 50 )

S.o.p ( "Second division" ) ;else if ( per >= 40 )

S.o.p ( "Third division" ) ;else

S.o.print ( "Fail" ) ;

One More Way

else is working for all three ifs


Logical Operators

&& - And|| - Or! - Not

Useful in

Checking Ranges

Yes / No Problem

class Insurance


int age ;System.out.printf ( "Enter age, sex, marital status" ) ;// receive age, s, msif ( ms == m )

S.o.p ( "Insured" ) ;else

if ( s == m )

if ( age > 30 )S.o.p ( "Insured" );

elseS.o.p ( "Not Ins." );

else

char s, ms ;

elseS.o.p ( "Not In." );

26 m u’ ’

’ ’

Not Insured

if ( age > 25 )S.o.p ( "Ins." ) ;

Using Logical Operatorsclass Insurance


int age ;char s, ms ;S.o.println ( "Enter age, sex, marital status" ) ;// receive age, s, ms

if ( ms = = ’m’ ms = = ’u’ s = = ’m’ age > 30ms = = ’u’ s = = ’f’ age > 25 )

elseSystem.out.println ( "Insured" ) ;

system.out.println ( "Not Insured" ) ;

)(||

||( )

)(&&&&

&&&&

26 m u

Not Insured


Working of && And ||

cond2cond1

True True

TrueTrue

False FalseFalseFalse

cond1 && cond2 cond1 || cond2

True TrueFalse FalseTrue FalseFalse True

Expression c2 goes to work if

boolean a ;int i = 7, j = 2 ;a = i < 5 && ++j > 6 ;System.out.print ( j ) ;

Short Circuit Operationsboolean a ;a = 2 && 3 ;

boolean a ;int i = 7, j = 2 ;a = i < 5 & ++j > 6 ;System.out.print ( j ) ;

2

3

c1 && c2 c1 & c2c1 || c2c1 | c2

c1 is trueAlwaysc1 is falseAlways

a = -3 + b - 5 ;

Hierarchy of OperatorsOperators Type

! Logical Not* / % Arithmetic

+ - Arithmetic< > <= >= Relational= = != Relational&& Logical And|| Logical Or= Assignment

Increasing Priority

Unary - Binary -

BinaryOperators


Conditional OperatorsYashavant Kanetkar

[email protected]

Objectives

Working of && and ||Short circuit operationsVariations of decision control instructionWhat are conditional operatorsWhen to use them

Working of && And ||

cond2cond1

True True

TrueTrue

False FalseFalseFalse

cond1 && cond2 cond1 || cond2

True TrueFalse FalseTrue FalseFalse True


Expression c2 goes to work if

boolean a ;int i = 7, j = 2 ;a = i < 5 && ++j > 6 ;System.out.print ( j ) ;

Short Circuit Operationsboolean a ;a = 2 && 3 ;

boolean a ;int i = 7, j = 2 ;a = i < 5 & ++j > 6 ;System.out.print ( j ) ;

2

3

c1 && c2 c1 & c2c1 || c2c1 | c2

c1 is trueAlwaysc1 is falseAlways

a = -3 + b - 5 ;

Hierarchy of OperatorsOperators Type

! Logical Not* / % Arithmetic

+ - Arithmetic< > <= >= Relational= = != Relational&& Logical And|| Logical Or= Assignment

Increasing Priority

Unary - Binary -

BinaryOperators

Exchanging Blocksclass Sample


int a = 3, b = 4 ;

if ( a <= b )S.o.p ( "A" ) ;

elseS.o.p ( "B" ) ;

Output: A if ( )

S.o.p ( "B" ) ;else

S.o.p ( "A" ) ;

a > b

Or


One More Wayclass Sample


int a = 3, b = 4 ;if ( a <= b )

S.o.println ( "A" ) ;else

S.o.println ( "B" ) ;

Output: A

a <= b a !> b

if ( ! ( a > b ) )S.o.println ( "A" ) ;

elseS.o.println ( "B" ) ;

Or

class sample


int a = 3, b = 4 ;if ( a > b )

S.o.println ( "B" ) ;else

S.o.println ( "A" ) ;

Output: A

Yet Another Way

Or

if ( ! ( a <= b ) )S.o.p ( "B" ) ;

elseS.o.p ( "A" ) ;

class Sample


int a = 3, b = 4, c ;if ( a <= b )

c = 10 ;else

c = 20 ;

Cond. Operators

? : - Conditional operatorsOnly Ternary Operators

a <= b ? c = 10 : c = 20 ;

Or

c = a <= b ? 10 : 20 ;


class Sample


int a = 3, b = 4, c ;if ( a <= b )

c = 10 ;

How Would You Convert

Error

a <= b ? c = 10 ;

Remove The Error

a <= b ? c =10 : ;

a <= b ? c = 10 : ; ;

Soln: c = a <= b ? 10 : 0 ;

Terminator Null Statement

Dummy

Necessary

Would This Workint a = 2, b = 4, c, d ;d = a <= b ? c = 10 : c = 20 ;System.out.println ( d ) ;

int a = 2, b = 4 ;a <= b ? S.o.println ( "Hi" ) ; S.o.println ( "Bye" ) ;

expression1 ? expression2 : expression3 ;

int a = 2, b = 4, c ;c = a <= b ? 10 : 20.5 ;

of same type


Moral of The StoryUse one, use anotherDummy expressionNot a replacement for if-else

Only 1 expression in ? partand one in : part

d = a <= b ? ( e = b > a ? 10 : 23 ): 20 ;

Nesting not allowed


Conversions & ComparisonsYashavant [email protected]

Objectives

Conversion between int and floatConversion between char and floatRepresentation of ints and charsASCII codes and ASCII valuesComparison of real values

int z ;float d = 6.8f ;z = ( int ) d ;

float to intConversions

class Conversions


int a = 10, b = 20 ;float c = 3.14f , d = 6.8f ;System.out.printf ( "%f %d", a, b ) ;System.out.printf ( "%d %d", c, d ) ;

Don’t use printf( ) for int to float or float to int conversionCarry out narrowing conversions using typecasting

float z ;int a = 10 ;z = a ;

int to float

Illegal format conversion exception


class Conversions


int i = 65, j = 90 ;char ch = ’A’, dh = ’Z’ ;System.out.printf ( "%d %d %c %c", i, j, ch, dh ) System.out.printf ( "%c %c", i, j ) ;System.out.printf ( "%d %d", ch, dh ) ;

Conversions Continued...

65 90 A Z

A Z

65 90

int to char conversions are reliablechar to int conversions are reliable

i a ch

int i = 65 ; float a = 3.14 ; char ch = ’A’ ;

01000001 0s & 1s 01000001

Binary Eqv. Binary Eqv. ASCII code

Representation

Same1 * 26 + 1 * 20

Every ASCII code is 8-bit code

S.o.printf ( "%d", ch ) ;

Methods Are Different

S.o.printf ( "%c", i ) ;

65

A

int i = 65 ;char ch = ’A’ ;

Only lower bytegets used

1 * 27 + 1 * 20

ch

Lowest00000000 01000001Highest

00000000 0100000100000000 00000000

i

Highest Lowest00000000 01000001


Surprised?

float a = 0.7f ;if ( a < 0.7 )

S.o.printf ( "A" ) ;else

S.o.printf ( "B" ) ;

A float a = 5.375f ;if ( a < 5.375 )

S.o.printf ( "A" ) ;else

S.o.printf ( "B" ) ;

B365 0.7

Integer Double

Binary of A Float

Binary of 5.375

Binary of 0.7

<32 - bitRecurring binary equivalent of 0.7

64 - bitRecurring binary equivalent of 0.7

Recurring

Non-Recurring

Truncated after 32/64 bits

==32 - bitNon-Recurring binary of 5.375

64 - bitNon-Recurring binary of 5.375

Similar to 1.333 < 1.333333

Similar to 2.5 == 2.50000

Safetyfloat a = 0.7 ;if ( a < 0.7f )

S.o.p ( "A" ) ;else

S.o.p ( "B" ) ;

B

float a = 5.375 ;if ( a < 5.375f )

S.o.p ( "A" ) ;else

S.o.p ( "B" ) ;

double a = 0.7 ;if ( a < 0.7 )

S.o.p ( "A" ) ;else

S.o.p ( "B" ) ;

double a = 5.375 ;if ( a < 5.375 )

S.o.p ( "A" ) ;else

S.o.p ( "B" ) ;

B

B

B

Compare 2 floats or 2 doubles


ASCII CodeCharacter Decimal

ASCII Codes

A 01000001B 01000010C 01000011D 01000100E 01000101.. ….

6566676869..

ASCII Values

Characters to be Represented26 Capital letters ( A- Z )26 Smallcase letters ( a - z )10 Digits ( 0 - 9 )32 Special Symbols ( + - * / . : ; etc. )34 Non-printable chars - control chars128 Graphic characters

256 Characters

00000000 To 11111111

ASCII Values26 Capital letters 26 Smallcase letters 10 Digits32 Special Symbols34 Non-printable chars128 Graphic characters

256 Characters

65 - 9097 - 12248 - 57

0 - 33128 - 255

0 - 25509 – Tab13 – Enter27 – Escape32 – Space


Repetition Control Instruction


ObjectivesRepetition Control InstructionGeneral form of whileIncrementation & Decrementation operatorsVariations of ++ and -- operators

Control Instructions

Decision - if - else- ? :- < > <= >= = = !=- && || !- & |

Repetition / Loop control instruction

Sequence


To Begin With...

S.o.p ( "Simple interest = Rs " + si ) ;

class Loop


S.o.p ( "Enter values of p, n, r" ) ;// receive valuessi = p * n * r / 100 ;

int p, n ;float r, si ;

Repetition...

S.o.p ( "Enter values of p, n, r" ) ;// receive valuessi = p * n * r / 100 ;S.o.p ( "Simple interest = Rs " + si ) ;

int p, n ; float r, si ;

while ( )

int i ; i = 1 ;

i <= 10

i = i + 1 ;

class Loop


class Loop


int i ;i = 1 ;while ( i <= 10 )

/* any logic */i = i + 1 ;

Logic Doesn’t Matter

// Initialisation of loop counter // Testing of loop counter

// Incrementation of loop counter

Loop counters can be int, long int, float or char

Loop counters can be incremented or decremented by any suitable step value

Loop Counter /Index variable


Another Program// Print numbers from 1 to 10 class PrintNumbers


int i = 1 ;while ( i <= 10 )

S.o.println ( i ) ;

i = i + 1 ;

i++ ;

Another way

++i ;

Another way

i = i + 1 i++i = i + 2 i+++i = i + 10 ?

++ Increases value of a variable by 1-- Decreases value of a variable by 1**//%%

Incrementation / Decrementation Operators

Don’t makesense

Tip : +++ doesn’t exist

Would This Worki = j---2 ; int i, j = 3 ;

i = --j ;i = --3 ;

i = j----2 ;i = j----2 ;

int i, j = 2, k = 3 ;i = ( j + k )++ ;

i = j-- - -2 ;

j = j - 1

3 = 3 - 1

j + k = j + k + 1

++ and - - can be done only on variables

CompulsoryOptional

i = j-- - 2 ;


The while LoopYashavant Kanetkar

[email protected]

Objectives

Pre incrementation and Post incrementationNuances of while loopCompound Assignment OperatorsUsage of break keywordRunning sums and products

Is i++ Same As ++i

int i = 1 ;while ( i <= 10 )

S.o.p ( i++ ) ;

int i = 1 ;while ( i <= 10 )

S.o.p ( ++i ) ;

0<

1O/p: 2 3 4……9 10 2 3 4 5……9 10 11O/p:

1 st oper. - Printing2 nd oper. - Incr.

i++ ; ++i ;printf ( "%d", i++ ) ; printf ( "%d", ++i ) ;

1 st oper. - Printing2 nd oper. - Incr.


Two More Ways

int i = 0 ;while ( i++ < 10 )

S.o.p ( i ) ;

int i = 0 ;while ( ++i <= 10 )

S.o.p ( i ) ;

1 st oper. - Testing2 nd oper. - Incr.

1 st oper. - Incr.2 nd oper. - Testing

Compare

int i = 1 ;while ( i <= 10 )

S.o.p ( i++ ) ;

int i = 0 ;while ( i < 10 )

S.o.p ( ++ i ) ;

int i = 0 ;while ( ++i <= 10 )

S.o.p ( i ) ;

int i = 0 ;while ( i++ < 10 )

S.o.p ( i ) ;

class PrintNum


int i = 1 ;while ( i <= 10 )

S.o.p ( i ) ;i += 1 ;

Print Nos. From 1 to 10a = a * 10 ;

a *= 10 ;

b = b % 5 ;

b %= 5 ;

+= -= *= /= %= Compound Assignment Oper.

Same as i = i + 1 i++ ++i


One More Wayclass PrintNum


int i = 1 ;while ( true ) /* Repeat infinite times */

S.o.p ( i ) ;i++ ;

if ( i > 10 )break ;

Keyword

break - Terminates Loopexit( ) - Terminates Program

if ( i > 10 )System.exit( 1 ) ;

Reason for termination

Calculate

n!nΣ ii = 1

xn

1 * 2 * 3 * 4 *….n

1 + 2 + 3 + 4 +.…n

2 * 2 * 2 * 2 *….n

Running sum

Running product

Running product

s = s + ;

Running Sum & Products

ip = p * i ;pr = pr * 2 ;

s = 0 ; p = 1 ; pr = 1 ;

1 + 2 + 3 + 4 +.…n RS1 * 2 * 3 * 4 *….n RP2 * 2 * 2 * 2 *….n RP

class SumProds

public static void main( ) throws Ex..

// receive nint s, p, pr, i, n ;

i = 1 ;while ( i <= n )

i++ ;

S.o.p ( s + " " + p + " " + pr ) ;

i s1 0

123364105156

5


The for LoopYashavant Kanetkar

[email protected]

Objectives

Sum of SeriesWorking of for loopComparison of while and for loopVariations of for loop

x1 x3 x5 x7 x9— - — + — - — + — - …………10 terms1! 3! 5! 7! 9!

main( )

// receive x

while ( i <= 10 ) calculate numerator

calculate denominatorterm = numerator / denominatorAdd / subtract alternate terms to/from s

i = 1 ; s = 0 ;

i++ ;print ( s ) ;


class Series


// receive xi = 1 ;while ( i <= 10 )

S.o.println ( s ) ;

i++ ; j = j + 2 ;s = ( i % 2 == 0 ) ? s - t : s + t ;

while ( k <= j )

d = d * k ; n = n * x ; k++ ;

k = n = d = 1 ;

t = n / d ;

float x, s, n, d, t ; int i, j, k, n ; x1 x3 x5 .. — - — + — -1! 3! 5! s = 0 ;

j = 1 ;

while ( i <= n - 1 )

if ( n % i == 0 )

S.o.p ( "Not a prime number" ) ;

i++ ;

class PrimeNumber


int n ;S.o.p ( "Enter a num." ) ;// receive n

if ( i == n )

break ;

S.o.p ( "Prime number" ) ;

13

Prime No.

13

2 3 4 .. .. .. 12

int i = 2 ;

Loop Control Instructionswhilefordo-while


The while Loopclass WhileLoop


int m1, m2, m3, avg, i ;i = 1 ;while ( i <= 10 )

// receive m1, m2, m3avg = ( m1 +m2 + m3 ) / 3 ;S.o.p ( avg ) ;i++ ;

Init Test IncrTestTest

IncrIncr

Test Incr.. .... ..

Init Test IncrTestTest

IncrIncr

Test Incr.. .... ..

class ForLoop


int m1, m2, m3, avg, i ;

// receive m1, m2, m3avg = ( m1 + m2 + m3 ) / 3 ;S.o.p ( avg ) ;

( )

The for Loop

for i++i = 1 ; i <= 10 ;

Comparision - I

int i = 1 ;while ( i <= 10 )

statement1 ;statement2 ;statement3 ;i++ ;

int i ;for ( i = 1 ; i <= 10 ; i++ )

statement1 ;statement2 ;statement3 ;

Finite LoopInfinite Loop


Comparison II

int i = 1 ;while ( i <= 10 ) ;

statement1 ;statement2 ;statement3 ;i++ ;

int i ;for ( i = 1 ; i <= 10 ; i++ ) ;


Finite LoopInfinite Loop

Comparison IIIint i = 1 ;while ( )


int i = 1 ;for ( ; ; )


Infinite LoopError

Print Nos. From 1 to 10

class PrintNumbers


int i ;for ( i = 1 ; i <= 10 ; i++ )

S.o.p ( i ) ;

Or i = i + 1 i++ ++i


Infinite loop

Dropping Init./Incr./Cond.int i = 1 ;for ( ; i <= 10 ; i++ )

S.o.p ( i ) ;

int i = 1 ;for ( ; i <= 10 ; )

S.o.p ( i ) ;i++ ;

int i = 1 ;for ( ; ; )

S.o.p ( i ) ;i++ ;

if ( i > 10 )break ;

S.o.p ( i++ ) ;

if ( ++i > 10 )

; ; Necessary


More for LoopsYashavant [email protected]

ObjectivesNested for loopsUsage of break and continueMultiple initialisations in for loop

1 1 1

1 1 2

1 1 3

1 3 11 3 21 3 3

1 2 11 2 21 2 3

3 1 1

3 1 2

3 1 3

3 2 1

3 2 2

3 2 3

3 3 1

3 3 2

3 3 3

2 1 1

2 1 2

2 1 3

2 2 1

2 2 2

2 2 3

2 3 1

2 3 2

2 3 3

Combinations


1 1 11 1 21 1 3

1 3 1

1 3 2

1 3 3

1 2 1

1 2 2

1 2 3

i = 1 ;j = 1 ;for ( k = 1 ; k <= 3 ; k++ )

S.o.p ( i + " " + j + " " + k ) ;

class Combinations


int i, j, k ;

Starting Off...i j k

class Combinations


int i, j, k ;i = 1 ;

for ( k = 1 ; k <= 3 ; k++ )S.o.p ( i + " " + j + " " + k ) ;

for ( j = 1 ; j <= 3 ; j++ )

Adding One More Loop

1 1 11 1 21 1 3

1 3 1

1 3 2

1 3 3

1 2 1

1 2 2

1 2 3

i j k

class Combinations


int i, j, k ;

for ( j = 1 ; j <= 3 ; j ++ )

for ( k = 1 ; k <= 3 ; k++ )S.o.p ( i + " " + j + " " + k ) ;

for ( i = 1 ; i <= 3 ; i ++ )

1 1 1.. .. .... .. ..1 3 3

2 1 1.. .. .... .. ..2 3 3

3 1 1.. .. .... .. ..3 3 3

Finishing Off...


Unique Combinationsclass Combinations


int i, j, k ;for ( i = 1 ; i <= 3 ; i++ )

for ( j = 1 ; j <= 3 ; j++ )

for ( k = 1 ; k <= 3 ; k++ )

S.o.p ( i + " " + j + " " + k ) ;

.. .. ..1 2 3.. .. ..1 3 2

.. .. ..2 1 3.. .. ..2 3 1

.. .. ..3 1 2.. .. ..3 2 1

if ( i != j && j != k && k != i )

if ( i != j != k )printf ( "%d %d %d", i, j, k ) ;

class Combinations


int i, j, k ;for ( i = 1 ; i <= 3 ; i++ )

for ( j = 1 ; j <= 3 ; j++ )

for ( k = 1 ; k <= 3 ; k++ )

S.o.p ( i + " " + j + " " + k ) ;

One More Way

i j k

1 1 1

2 1

13

if ( i = = j || j = = k || k = = i )

elsebreak ;

class Combinations


int i, j, k ;for ( i = 1 ; i <= 3 ; i++ )

for ( j = 1 ; j <= 3 ; j++ )

for ( k = 1 ; k <= 3 ; k++ )

S.o.p ( i + " " + j + " " + k ) ;

The Correct Wayi j k1 1 1

23

123

24

if ( i = = j || j = = k || k = = i )

elsecontinue ;


Alternate Wayclass Combinations


int i, j, k ;for ( i = 1 ; i <= 3 ; i++ )

for ( j = 1 ; j <= 3 ; j++ )

for ( k = 1 ; k <= 3 ; k++ )

S.o.p ( i + " " + j + " " + k ) ;

if ( i = = j || j = = k || k = = i )

elsecontinue ;

for ( .. ; .. ; k++ )

if ( condition )continue ;

elsea = 2 ;

S.o.p ( "Hello" ) ;

Would ; be OK?

coninue abandons rest of the instructions in the loop

Multiple Initializationsint i, j, k ;i = 1 ; j = 3 ;for ( k = 1 ; k <= 5 ; k++ )

……i += 2 ;j *= 4 ;

for ( i = 1, j = 3, k = 1 ; k <= 5 ; i += 2, j *= 4 )

……

MultipleConditions?

Can I Drop k++

Connect using && and ||

Better Way


do while LoopsYashavant Kanetkar

[email protected]

ObjectivesFlexible declarationsSophisticated break and continuedo-while LoopEffects of break / continue on different loopsRepeating unknown number of times

Flexible Declarationsclass Myscope


for ( int i = 0 ; i < 3 ; i++ )

System.out.println ( i ) ;System.out.println ( i ) ;


Sophisticated breakclass Mybreak


for ( int i = 0 ; i < 3 ; i++ )

for ( int j = 0 ; j < 4 ; j++ )

for ( int k = 0 ; k <= 5 ; k++ )

……if ( i + j + k > 21 % 4 )

break ;

first : for ( int i = 0 ; i < 3 ; i++ )

break first ;

Sophisticated continueclass Mycontinue


for ( int i = 0 ; i < 3 ; i++ )

for ( int j = 0 ; j < 4 ; j++ )

for ( int k = 0 ; k <= 5 ; k++ )

……if ( i + j + k > 21 % 4 )

continue ;

first : for ( int i = 0 ; i < 3 ; i++ )

continue first ;

Type of Loops

whilefordo - while


The do-while Loopclass Loop


int i = 1 ;do

System.out.println ( i ) ;i++ ;

while ( i <= 10 ) ;

Tip1: - NecessaryTip2: ; after while - Necessary

Compare

do

S.o.p ( "Hi" ) ; while ( 4 < 1 ) ;

for ( ; 4 < 1 ; )S.o.p ( "Hi" ) ;

while ( 4 < 1 )S.o.p ( "Hi" ) ;

Hi No output No output

while ( …. )

if ( cond1 )break ;

if ( cond2 )continue ;

for ( .. ; .. ;… )if ( cond1 )

break ;if ( cond2 )

continue ;

do

if ( cond1 )break ;

if ( cond2 )continue ;

while ( …. ) ;

Effects of break & continue

if ( cond )

..

..break ;..

if ( cond )

..

..continue ;..

for ( .. ; .. ; .. )

..

..break ;..

for ( .. ; .. ; .. )

..

..continue ;..


while ( )

Unknown No. of Times

char ch = ’y’ ;ch == ’y’

class Unknown


/* some logic */System.out.println ( "Continue y / n" ) ;// receive ch

Try writing same using for / do - while

Foolproof?

while ( ch == ’y’ || ch == ’Y’ )


case Control InstructionYashavant Kanetkar

[email protected]

Objectivescase Control InstructionNuances of case Control InstructionVariations of case Control Instruction

Control InstructionsSequence DecisionRepetition

- while, for, do-whilebreak, continue

- ++ --- += -= *= /= %=

Case


class Example


int n ;S.o.p ( "Enter no. between 1 and 3" ) ;// receive n if ( n = = 1 )

S.o.p ( "You entered 1" ) ;else

if ( n = = 2 )S.o.p ( "You entered 2" ) ;

else

if ( n = = 3 )S.o.p ( "You entered 3" ) ;

elseS.o.p ( "Wrong choice" ) ;

Three Problems

Alternatives- Use &&, II- Use case CI

class Example


int n ; S.o.p ( "Enter no. between 1 and 3" ) ;// receive n

case 1 :

S.o.p ( "You Entered 1" ) ;case 2 :

S.o.p ( "You Entered 2" ) ;case 3 :

S.o.p ( "You Entered 3" ) ;else

S.o.p ( "Wrong Choice" ) ;

switch ( n )

If a case fails control jumps

to the next case

class Example


int n ; S.o.p ( "Enter no. between 1 and 3" ) ;// receive n

case 1 :

S.o.p ( "You entered 1" ) ;case 2 :

S.o.p ( "You entered 2" ) ;case 3 :

S.o.p ( "You entered 3" ) ;

switch ( n )

default :S.o.p ( "Wrong Choice" ) ;

2

Output:You entered 2


class Example


int n ;// receive nswitch ( n )

case 1 : S.o.p ( "You entered 1" ) ;

case 2 :S.o.p ( "You entered 2" ) ;

case 3 :S.o.p ( "You entered 3" ) ;

default : S.o.p ( "Wrong choice" ) ;

Tip: If a case is satisfied all statements below it upto of switch are executed

Output:You entered 2You entered 3Wrong choice

2

class Example



case 1 :S.o.p ( "You Entered 1" ) ;




The Solution

break ;

break ;

break ;

2

- break terminates a switch- are optional even if there are

multiple statements in a case

class Example



case 1 :S.o.p ( "You Entered 1" ) ; break ;

case 2 :S.o.p ( "You Entered 2" ) ; continue ;



What If continue

2break - Loops, switchcontinue - Loops

Illegal


class Example


int n ;// receive n switch ( n )


case 1 : S.o.p ( "You Entered 1" ) ; break ;


default :S.o.p ( "Wrong choice" ) ;

Tip: Order of cases is unimportant

class Example







Tip: Even default can bethe very first case

break ;

class Example





case 3 : S.o.p ( "You Entered 1" ) ;

Tip: default case is optional


Nuances Of caseControl Instruction


Objectives

Nuances of case Control InstructionGeneral form What all can be checkedMenu driven programs

class Example


char ch ;S.o.p ( "Enter alphabet between A and C" ) ;// receive chch = str.charAt ( 0 ) ;switch ( ch )

case 'A' :S.o.p ( "You entered A" ) ; break ;

case 'B' :S.o.p ( "You entered B" ) ; break ;

case 'C' :S.o.p ( "You entered C" ) ; break ;

What if ‘a’, ‘b’, ‘c’


class Example


char ch ;S.o.p ( "Enter alphabet between A and C" ) ;// receive chswitch ( ch )

case 'A' || 'a' : S.o.p ( "You entered A" ) ; break ;

case ’B’ || ’b’ :S.o.p ( "You entered B" ) ; break ;

case ’C’ || ’c’ :S.o.p ( "You entered C" ) ; break ;

Error

class Example


char ch ;S.o.p ( "Enter alphabet between A and C" ) ;// receive chswitch ( ch )

case ’A’ :S.o.p ( "Entered A" ) ; break ;

case ’B’ :S.o.p ( "Entered B" ) ; break ;

case ’C’ :S.o.p ( "Entered C" ) ; break ;

switch ( ch )

case 23 :case 4 :case -55 :

S.o.p ( ".." ) ;break ;

Acase ’a’ :

case ’b’ :

case ’c’ :

a

Case Conversion not useful for numbers

int n = 2 ;int a = 1, b = 2 ;switch ( n )

case a :…

case b :…

case 3 :…

Would This Work


n + 3 / a + 24 + 3 / 5 + 2

3 + 2 % 5a + b % c

General Form

switch ( expression )

case constant expression :…



default : …

Checking switch

intcharlong intfloatdouble

Is switch a replacement for if ?

Which worksfaster ?

class Menu


S.o.p ( "1. Odd / Even" ) ;S.o.p ( "2. Leap year" ) ;S.o.p ( "3. Prime number" ) ;S.o.p ( "0. Exit" ) ;S.o.p ( "Your choice?" ) ;// receive choice.. ..

int choice ;1. Odd / Even2. Leap Year3. Prime No.0. ExitYour Choice?

Menu Management


class Menu


int choice ;// display menu // receive choice

switch ( choice )

case 1 : // odd / even logicbreak ;

case 2 :// leap year logicbreak ;

default :S.o.p ( "wc" ) ;

case 3 ://prime no. logicbreak ;

case 0 :break ;

Odd / Even logicoddeven.java

Ctrl C, Ctrl V

No while, No Menu

while ( 1 )

/*display menu*/// receive choice switch ( choice )

case 1 :…break ;

case 0 :break ;

class Menu


int choice ;

System.Exit ( 1 ) ;

RequirementsInfinite whileswitch

Conclusion

Any logic can be programmed using: SequenceDecisionRepetitionCase


FunctionsYashavant Kanetkar

[email protected]

ObjectivesWhat are functionsProgram with multiple functionsHow to define functionsHow to call functionsDifferent types of function calls

Functionsclass Functions


S.o.p ( "\n I am in main" ) ;public static void bombay( )

S.o.p ( "\n I am in Bombay" ) ;

public static void kanpur( )

S.o.p ( "\n I am in Kanpur" ) ;

Output:I am in main

main( )println( )print( )printf( )exit( )for( )while( )if( )switch( )

Functions


Calling Functions


S.o.p ( "\n I am in main" ) ;

public static void bombay( )

S.o.p ( "\n I am in Bombay" ) ;public static void kanpur( )

S.o.p ( "\n I am in Kanpur" ) ;

I am in mainI am in BombayI am in Kanpur

bombay( ) ; kanpur( ) ;

Output :

Function Call

Function Def.

class Functions

Types of Functions

printf( )println( )print( )exit( )

kanpur( )bombay( )main( )

Std. LibraryReady-made

User-definedDefined by us

TipsA Java program can contain one or more classes

Each class can contain multiple functions

Execution always begins with main( ) of Main class

One of the class has to be marked as Main class


Nobody is Nobody’s Boss

public static void kanpur( )

S.o.p ( "\n I am in Kanpur" ) ; bombay( ) ;

class Functions


S.o.p ( "\n I am in main" ) ;bombay( ) ; kanpur( ) ;


S.o.p ( "\n I am in Bombay" ) ;kanpur( ) ;

Any function can callany other function

Order, Order !class Functions


S.o.p ( "\n I am in Bombay" ) ;public static void main( )

S.o.p ( "I am in main" ) ;bombay( ) ;

Tip: Functions can bedefined in any order

More Calls, More Billsclass Functions


int i ;S.o.p ( "\n In main" ) ;for ( i = 1 ; i <= 20 ; i++ )

bombay( ) ;public static void bombay( )

S.o.p ( "\nIn Bombay" ) ;

Tip: More the calls, slower the execution

class Functions


int i ;S.o.p ( "\n In main" ) ;bombay( ) ;


for ( i = 1 ; i <= 20 ; i++ ) S.o.p ( "\nIn Bombay" ) ;

Better


Types of Calls// pr1.javapublic static void main( )

bombay( ) ;main( ) ;fun1( ) ;fun2( ) ;


S.o.p ( "\n In Bombay" ) ;

// pr2.javapublic static void fun1( )

..

..

..

// pr3.java on m/c Alpha public static void fun2( )

..

..

HH

Local Call - Recursive Call. Process - RecursionSTD call - Calling function in another fileISD Call - Calling function in another m/c

Happy Hours - Calling function in same file

ISD

STDLC


Communication Using Functions


ObjectivesHow to communicate between functionsPassing values and controlReturning value and controlReturning multiple values from a function

Communicationclass Communication


int a = 10, b = 20, c = 30 ;calsum( ) ;System.out.println ( s ) ;

public static void calsum( )

int a, b, c, s ;

int s ;

System.out.println ( s ) ;s = a + b + c ;

0

0


class Communication


int a = 10, b = 20, c = 30 ; int s ; calsum ( ) ;System.out.println ( s ) ;

public static void calsum ( )

int s ;

System.out.println ( s ) ;s = x + y + z ;

a, b, c

int x, int y, int z

Passing Values

60

Actual & Formal args must match in Number, Order and Type

ActualArguments

Formal Arguments

0

class Communication


int a = 10, b = 20, c = 30, s ; calsum ( a, b, c ) ;

public static int calsum ( int x, int y, int z )

int ss ;ss = x + y + z ;return ( ss ) ;

S.o.p ( s ) ;

Returning Values

60

return ( ss ) ;return ( 60 ) ;return ( x + y + z ) ;

return ; Returns only control

Returns only value

s = calsum ( a, b, c ) ; Return control and value

x = calsum ( a, 25, d ) ;calsum ( 10 + 2, 25 % 3, d ) ;calsum ( a, calsum ( 25, 10, 4 ), d ) ;d = calsum ( a, 25, d ) * calsum ( a, 25, d ) + 23 ;

Are These Calls OK?

public static int calsum ( int x, int y, int z )

int ss ;ss = x + y + z ;return ( ss ) ;

• Actual arguments - constants / variables / expressions• Formal arguments - variables• Nested calls are legal• Call within an expression is legal

Returned value can be ignored


class ReturnTwo


int a = 10, b = 20, c = 30 ;

S.o.p ( s + " " + p ) ;int sumprod ( )int x, int y, int z

ss = x + y + z ;pp = x * y * z ;

sumprod ( a, b, c ) ; s, p = sumprod ( a, b, c ) ;

int ss, pp ;

return ( ss, pp ) ;

Returning More Than 1 Value

int s, p ;

A function can return only 1 value at a time

class ReturnTwo


int a = 10, b = 20, c = 30 ;int s, p ; s = sumprod ( a, b, c ) ;p = sumprod ( a, b, c ) ;System.out.println ( s + " " + p ) ;

public static int sumprod ( int x, int y, int z )

ss = x + y + z ;pp = x * y * z ;return ( ss ) ;return ( pp ) ;

int ss, pp ;

One More Try

60 60

Redundant

class ReturnTwo


int a = 10, b = 20, c = 30 ; int s, p ; s = sumprod ( a, b, c ) ;p = sumprod ( a, b, c ) ;System.out.println ( s + " " + p ) ;

, 1, 2

public static int sumprod ( int x, int y, int z, )

ss = x + y + z ; pp = x * y * z ;int ss, pp ;

int code

if ( code == 1 ) return ( ss ) ;

elsereturn ( pp ) ;

The Only Way Out

Sum, Product,Average, VarianceStandard Deviation

60 6000


A Better Waypublic static int sumprod ( int x, int y, int z, int code )

ss = x + y + z ;pp = x * y * z ;

int ss, pp ;

if ( code == 1 ) return ( ss ) ;

elsereturn ( pp ) ;

code == 1 ? return ( x + y + z ) : return ( x * y * z ) ;

return ( code == 1 ? x + y + z : x * y * z ) ;


More About FunctionsYashavant [email protected]

ObjectivesExamples of functionsReturning a non-integer valueDifferent return typesBeyond basic Arithmetic


S.o.println ( "Enter year" ) ;// receive y

int y ;

romanize ( y ) ;public static void romanize ( int yy )

int n, i ;n = yy / 1000 ;for ( i = 1 ; i <= n ; i ++ )

S.o. println ( "m" ) ;

Decimal Roman1000 m

500 d100 c

50 l10 x

5 v1 i

Roman Equivalent1998 m d c c c c l x x x x i i i

1998

v class RomanEqu


public static void romanize ( int yy )

romanize ( y ) ;

class RomanEqu


S.o.println ( "Enter year" ) ;// receive y

int y ;

int n, i ;n = yy / j ;for ( i = 1 ; i <= n ; i ++ )

S.o.println ( ) ;

ch

, int j , char ch

return ( yy % j ) ;

, 1000 , ’m’

General Call

y = romanise ( y, 1000, ’m’ ) ;

int

y = romanise ( y, 500, ’d’ ) ;y = romanise ( y, 100, ’c’ ) ;y = romanise ( y, 50, ’l’ ) ;y = romanise ( y, 10, ’x’ ) ;y = romanise ( y, 5, ’v’ ) ;romanise ( y, 1, ’i’ ) ;

, int j , char ch


..., ’m’

public static int romanize ( int yy )

int n, i ;n = yy / j ;for ( i = 1 ; i <= n ; i ++ )

System.out.println ( ch ) ;return ( yy % j ) ;

y = romanise ( y, 1000 ) ;1998 m d c c c c l x x x x i i i v

Error:Cannot find symbol

seWorks

public static float square ( float x )

b = square ( 2.5f ) ;c = square ( 1.5f ) ;S.o.p ( a + " " + b + " " + c ) ;

a = square ( 2.0f ) ;

Returning a Non-Intclass SquareNum


float y ;y = x * x ;return ( y ) ;

4.0 6.25 2.25

float a, b, c ;

FunctionCall

FunctionDefinition


Return Types

Error

Nothing isreturned

Error

Error

public class PrePost

public static void main ( String[ ] args )

int i = 3 ;

S.o.printf ( "%d %d", ++i, i ) ;S.o.printf ( "%d %d", i, ++i ) ;

4 5

Output?

4 4

Beyond Basic Arithmeticjava.lang package contains a Math classMath class contains methods and constantsTypes of methods

Basic methodsExponential and logarithmic methodsTrignometric methods


public class MathFunctions


double a = -792.735, b = 43.74 ;int i = 15, j = 45;

S.o.p ( Math.abs ( a ) ) ;S.o.p ( Math.ceil ( b ) ) ;S.o.p ( Math.floor ( b ) ) ;S.o.p ( Math.rint ( b ) ) ;S.o.p ( Math.max ( i, j ) ) ; S.o.p ( Math.min ( i, j ) ) ;

Basic Arithmetic Functions

792.73544.043.044.04515

public class ExpLogFunctions


double a = 3 ;double b = 2 ;

S.o.p ( Math.E ) ;S.o.p ( Math.exp ( a ) ) ;S.o.p ( Math.log ( a ) ) ;S.o.p ( Math.pow ( a, b ) ) ;S.o.p ( Math.sqrt ( a ) ) ;

Exp and Log Functions

2.71828182845904520.0855369231876681.09861228866810989.01.7320508075688772

public class TrigFunctions


double d = 45.0 ;double r = Math.torad ( d ) ;

S.o.p ( Math.PI ) ;S.o.p ( Math.sin ( r ) ) ;S.o.p ( Math.cos ( r ) ) ;S.o.p ( Math.tan ( r ) ) ;S.o.p ( Math.toDegrees ( Math.asin ( Math.sin ( r ) ) ) ) ;S.o.p ( Math.toDegrees ( Math.acos ( Math.cos ( r ) ) ) ) ;S.o.p ( Math.toDegrees ( Math.atan ( Math.tan ( r ) ) ) ) ;

Trignometric Functions

3.1415926535897930.70710678118654750.7071067811865476145.045.045.0


public class RandomNum


int num ;num = ( int ) ( Math.Random( ) * 20 ) ;S.o.p ( num ) ;num = 50 + ( int ) ( Math.Random( ) * 10 ) ;S.o.p ( num ) ;

Random Numbers

357


RecursionYashavant Kanetkar

[email protected]

ObjectivesWhat is Recursion

Programs using Recursion

Pros and Cons of using Recursion

When to use it

Recursion – Different Forms

class Recursion


fun( ) ;public static void fun( )

System.out.printf ( "Hi" ) ;fun( ) ;

Infinite Loop

Stops when Stack overflow occurs


More Generalclass SumOfDigits


int num, sum ;S.o.p ( "Enter a number" ) ;// receive num

public static int sumdig ( int n )

int d ; int s = 0 ; while ( )

n != 0

d = n % 10 ; n = n / 10 ; s = s + d ;return ( s ) ;

31698d5

485d3

n s d327 0 732 7 23 9 30 12

sum = sumdig ( num ) ;S.o.p ( sum ) ; 12

327

class SumOfDigits


S.o.p ( "Enter a number" ) ;// receive num

int num, sum ;

int rsum ( int n )

int d ; int s ; if ( )

n != 0

d = n % 10 ; s = d + rsum ( n ) ; n = n / 10 ;else

return ( 0 ) ; return ( s ) ;

327sum = rsum ( num ) ;S.o.p ( sum ) ;

4!

4 * 3 * 2 * 1

4 * 3 !

3 * 2 !

2 * 1 !

1 * 0 !

Fresh set of variables are born during each callVariables die when control returns

if ( )

n != 0d =

s =n =

else


int rsum ( int n )

int rsum ( int n )

if ( )

n != 0d =

s =n =

else


int rsum ( int n )

if ( )

n != 0d =

s =n =

else


327 % 10 ;327 / 10 ;7 + rsum ( 32 ) ;

int rsum ( int n )

if ( )

n != 0d =

s =n =

else


32 % 10 ;32 / 10 ;2 + rsum ( 3 ) ;

3 % 10 ;3 / 10 ;3 + rsum ( 0 ) ;

327


Factorial Valueclass FactorialOfNum


System.out.printf ( "Enter a number" ) ;// receive num

int num, fact ;

fact = factorial ( num ) ;S.o.p ( fact ) ;

public static int factorial ( int n )

int p = 1 ; while ( )

n != 0

p = p * n ; n-- ;

return ( p ) ;

Recursive Fact. class FactorialOfNum


S.o.p ( "Enter no." ) ;// receive num

int num, fact ;

fact = refact ( num ) ;S.o.p ( fact ) ;

public static int refact ( int n )

int p ; if ( )n != 0

p = n * refact ( n - 1 ) ;

return ( p ) ;

elsereturn ( 1 ) ;

Recursion TipsMake recursive call in an ifelse block is escape routeelse contains end cond. logicreturn may not be presentToo many calls – Stack FullAdv. - Ease Speed

Difficult to:UnderstandExplainWrite aboutMaintain


Peg A Peg B Peg C

3 ! + 1

A B CA to C

A B CA to B

A B CC to B

A B CA to C B to A

A B C

B to CA B C

A to CA B C


Object Oriented Programming


Objectives

What is object-oriented programmingHow OO model applies to programmingDifference between class and object How to create classes and objectsHow to use objects

What is this?It is a vehicle It is my bike Object may contain other objects

Engine, Gearbox, Brake, Lights

Contents

Real-World Model

DataOil Temp.Oil densityRPMTiming detailsType of fuel

FunctionsIgniting fuelMoving pistonOpening valvesEjecting burnt fuelRotating crank

PropertiesProcedures

GenericClass

SpecificObject


DateTime Class

More Classes and Objects

Datadd, mm, yyh, m, s

Functionsgetdate( )gettime( )setdate( )settime( )

Object d1- 13/12/2007- 12:25:30sd( ), gd( ), …

Object d2- 10/02/2009- 11:10:15sd( ), gd( ), …

Pop

Top

1020

Working Of Stack

EmptyTop

Push 10

Top 10

EmptyTop

Push 20

Top

1020

Pop

Top 10

push( ), pop( ) push( ), pop( )

- 5 elements- top = 4

- 7 elements- top = 6

Object s2Object s1

Stack Class

Stack Class & Stack Objects

DataArrayTop

FunctionsPush( )Pop( )Printall( )


package classdemo ;public class ClassDemo

public static void main ( String[ ] args)

Sample a, b ;a = new Sample( ) ;a.i = 10 ; a.j = 3.14f ;S.o.p ( a.i + " " + a.j ) ;b = new Sample( ) ;b.i = 20 ; b.j = 6.28f ;S.o.p ( b.i + " " + b.j ) ;

Creation of Classes & Objects

a

i j10 3.14

Objects are created using new operatora, b - References to Objectsa, b contain addresses of objects

class Sample

int i ;float j ;

i j

b

20 6.28

20 6.28

10 3.14

package classdemo ;public class ClassDemo


Sample a, b ;a = new Sample( ) ;a.SetData ( 10, 3.14f ) ;a.ShowData( ) ;b = new Sample( ) ;a.SetData ( 20, 6.28f ) ;b.ShowData( ) ;

Better Way... class Sample

private int i ;private float j ;public void SetData ( int ii,

float jj )

i = ii ; j = jj ;public void ShowData( )

S.o.p ( i + " " + j ) ;

a

i j10 3.14

i j

b

20 6.28pri., pub. - Access SpecifiersDefault - publicSafer and Better organised

s2 = new Sample( ) ;// receive x

Which Is Better

if ( x > 0 )

if ( x > 0 )

s1.age = x ;

class Sample

private int age ;public void setdata ( int x )

age = x ;

class Demo


Sample s1, s2 ; int x ;

if ( x > 0 )

s2.age = x ;

class Sample

public int age ; class Demo


sample s1, s2 ; int x ;s1 = new Sample( ) ;// receive x

// receive x

s2 = new Sample( ) ;s2.setdata ( x ) ;

s1 = new Sample( ) ;s1.setdata ( x ) ;// receive x

Better


Classes And Objects


Objectives

Handling Complex NumbersDifference between primitive and objectWhere objects are createdStack versus HeapThe this Reference

Handling Complex Numbers

On Addition 3.9 + 3.4i

On Subtraction 0.3 + 1.2i

2.1 + 2.3i1.8 + 1.1i

Real Part Imaginary Part

Function Add

Function Sub

Complex Class

2.1 2.3

Add( ) Sub( )

Complex Object1

1.8 1.1

Add( )

Complex Object2

Sub( )

Generic Unique


r i

public class ClassDemo

public static void main ( String[ ] args)

Complex a, b ;a = new Complex( ) ;a.SetData ( 2.1f, 2.3f );a.ShowData( ) ;b = new Complex( ) ;b.SetData ( 1.8f, 1.1f ) ;b.ShowData( ) ;

package classdemo ;class Complex

private float r, i ;public void SetData (

float rr, float ii )

r = rr ; i = ii ;public void ShowData( )

S.o.p ( r + " " + i ) ;

Implementation

r i1.8 1.1

2.1 2.3

2.1 2.3

1.8 1.1

private inaccessible from outsideAny class member can access other

a

b

How Many Copies

public void SetData ( .. )

r = rr ; i = ii ;public void ShowData( )

S.o.p ( r + " " + i ) ;

Common

Member FunctionsConceptually - ManyPractically - One

r i1.8 1.1

r i2.1 2.3

a

b

this400500

class ex

private int i ; private float a ;

public void SetData ( int ii, float aa )

this.this.a = aa ;

i = ii ;

The this Reference

i a

500

o2

504

i a

400 404

o1


ex e1 = new ex( ) ;

e1.SetData ( 5, 5.5f ) ;

e2.SetData ( 10, 10.5f ) ;

ex e2 = new ex( ) ;

class Sample

Can't be modifiedOptional

e1 is also passed

void SetData ( ex final this, int ii, float aa )


this.this.

Is this Necessary

i a

i a

500

400o2

404

504

o1public void SetData ( int i, float a )

class ex private int i ;

private float a ;

a = a ;i = i ;


ex e1 = new ex( ) ;ex e2 = new ex( ) ;e1.SetData ( 5, 5.5f ) ;

e2.SetData ( 10, 10.5f ) ;

class Sample


Java Member FunctionsYashavant [email protected]

ObjectivesWhat are constructorsWhat are overloaded functionsTypes of calls – By value, By referenceGarbage collection

Recap…Classes are like DatatypesObjects are specific instance of a classMultiple objects enjoy different data but share same func.Data is usually privateMember functions are usually publicObjects are namelessObjects are created using newObjects are referred using referencesReferences are created on stackObjects are created on heapthis reference is passed to member functions


Constructorsclass ex

private int i ; private float j ;

public ex ( int ii, float jj )

class Sample


ex e1 = new ex ( 10, 3.14f ) ;ex e2 = new ex( ) ;

i = ii ; j = jj ;ex( )

i = 0 ;

j = 0.0f ;

Object CreationAllocate space in memoryCall the constructor

i j

e1

10 3.14

i j

e2

0 0.0

2 ArgumentConstructor

0 ArgumentConstructor

OverloadedFunctions

Constructor TipsName of constructor must be same as name of classCtor is invoked only using newCtor is a functionCtor never returns any typeCtor can be overloadedIf the class is empty compiler inserts a CtorEither I do it or you do it policy

Different return types notenough for overloading

Fun.Overloading static void set ( int i, float j ) static void set ( float jj, int ii )static int set ( float jj, int ii )

class Sample


set ( 10 ) ;set ( 10, 3 ) ;set ( 10, 3.14f ) ;set ( 3.14f, 10 ) ;set ( 3.14f, 10 ) ;

Arguments must differ in

Number OrderType

static void set ( int i )static void set ( int i, int j )


Call By valueclass Sample


int i = 1 ;float f = 3.1f ;fun ( i, f ) ;S.o.p ( i + " " + f ) ;

void fun ( int ii, float ff )

ii = ii * 2 ;ff = ff * 2 ;S.o.p ( ii + " " + ff ) ;

Changing Formal arguments doesn't

change Actual arguments

1 3.1

2 6.2

Call By Referenceclass ex

private int i ; private float f ;

class Sample


ex e = new ex e.Set ( 1, 2.5f ) ;e.Display( ) ;

void fun ( ex p )

p.Set ( 3, 8.5f ) ;

void Display( )

S.o.p ( i + " " + f ) ;

fun ( e ) ;e.Display( ) ;

public Set ( int x, float y )

i = x ; f = y ;

1 2.5

3 8.5

i j

e

1 2.5

p

Objects are always passed by RefReference is passed by value

3 8.5

References

Complex c1, c2 ; c1 = new Complex( ) ;c2 = c1c1 = null ;

Complex Obj.

i fc1

c2 = null ;

c1 null

GCCommon for all programsPart of Java Runtime Env.

Shallow Copy Destroyed byGarbage Collector

c2

c2 null


Static FunctionsYashavant [email protected]

ObjectivesHow to share data amongst objectsStatic data and static functionsWhat is a Singleton classNeed for a Singleton classfinalize( ) method

class Ex

private int i ;private static int count = 0 ;

Ex( )

i = 0 ;count += 1 ;

static void ShowCount( )

S.o.p ( count ) ;

class Sample


Shared Data

• static functions can access only static data• static functions cannot call instance functions

e1 e2

i0 0

i

1

Ex e2 = new Ex( ) ;Ex.ShowCount( ) ;

2

Ex e1 = new Ex( ) ;

2count

Ex.ShowCount( ) ;


Only one object gets created from a classHint:- Create private constructor- Create static member function to create object

Problem

Singleton Class

Design Pattern

class Singleton

Singleton p ;

static Singleton Create( )

private Singleton( )

class Sample


Singleton s1 ;s1 = new Singleton( ) ;

Singleton Class

Singleton s2 ;s2 = Singleton.Create( ) ;

s1 = Singleton.Create( ) ;

s1 s2

if ( p == null )p = new Singleton( ) ;

return p ;

static Singleton p ;

p

Circle ClassCreate a Circle classEach Circle object will have a radius and colorProvide a function Area( ) to calculate area of circleCount how many objects of Circle class have been created

3count

3.14PI

colorR

radius1.5

Object1

colorG

radius1.1

Object2

colorB

radius1.4

Object3

Common for all objects


Circle ( float rr, int cc )

rad = rr ;color = cc ;count += 1 ;

Circle c1, c2, c3 ;c1 = new Circle ( 1.5, 'R' ) ;c2 = new Circle ( 1.1, 'G' ) ;c3 = new Circle ( 1.4, 'B' ) ;c1.Area( ) ;Sample.ShowCount( ) ;

class Circle

private int color ;private float rad ;private static int count ;final float PI = 3.14f ;

static void ShowCount( )

S.o.p ( count ) ;

class Sample


Implementation

void Area( )

S.o.p ( PI * rad * rad ) ;

Invoked using Object

Access PrivateData / Functions

FunctionType

Within class scope

Instance

Static

Summary

only static

Static functions can be called before creating

an object

class Ex

static int x, y, z ;

static void fun( )

static

x = 10 ; y = 20 ;z = x * 2 + y * 5 ;

class Sample


Ex.fun( ) ;

Static Block

S.o.p ( x ) ; S.o.p ( y ) ;S.o.p ( z ) ;

10 20 120

Static block gets executed exactly once whenthe class is loaded


finalize( ) MethodCalled when an object is about to be destroyedDestruction is done by Garbage CollectorUsed to free non-Java resource like file handle of fontCalled by Java Runtime just before garbage collectionNot called when an object goes out of scope

protected void finalize( )

// finalisation code


ArraysYashavant [email protected]

Objectives

What are Arrays

Need for Arrays

Properties of Arrays

Array Initialisation

Variable Sized Arrays

How Much Java

10 %? 20 % ? 30 %?

Data Typesint charfloat doublelong shortbyte boolean

Control Instr.if elsefor while do break continue switchcase default

Otherthrows classprivate public final importpackage newstatic thisvoid return30 / 48


Storing Multiple Valuesclass Array

S.o.p ( "Enter Marks" ) ;// receive m1, m2, m3 per = ( m1 + m2 + m3 ) / 3 ;S.o.p ( per ) ;

int m1, m2, m3, per ;

for ( i = 1 ; i <= 10 ; i++ )

int i ;

S.o.p ( per ) ;


Arraysclass Array

int m1, m2, m3, i ;int per[ ] = new int[ 10 ] ;

S.o.p ( per[ i ] ) ;

S.o.p ( "Enter Marks" ) ;// receive m1, m2, m3 per[ i ] = ( m1 + m2 + m3 ) / 3 ;

for ( i = 0 ; i <= 9 ; i++ )


for ( i = 0 ; i <= 9 ; i++ )

int [ ] per per = new int [ 10 ] ;

int per[ ] ;per = new int[ 10 ] ;

per - ReferenceArray is created on heap

Array Initialisation

c[ 5 ] = 3 + 7 % 2 ; c[ 6 ] = c[ 1 ] + c[ 3 ] / 16 ;

int a[ ] = 7, 6, 11, -2, 26 ;int b[ ] = new int[ 10 ] ;int c[ ] = 16, 13, -8, -7, 25 ;10S.o.p ( a[ 0 ] + " " + b[ 0 ] ) ;// receive c[ 7 ], c[ 8 ], c[ 9 ]

int i ;i = 2 ; int i = 2 ;

7 0

class Array public static void main( ) throws Exception

compulsory


Different types of arrays are possible – int, float, etc.

Tips About ArraysCollection of similar elements

30 20 16 18 35a[0] a[1] a[2] a[3] a[4]

402 406 410 414 418int a[ ] = 30, 20, 16, 18, 35 ;

Elements are stored in adjacent memory locations

a[ ] = 2, 1.4, ’A’, 6 ; int

int a[ ] = 11, 3, 6, 9 ;float b[ ] = 1.1f, 1.2f, 1.7f ;

11 3 6 9 1.1 1.2 1.7

Bounds checking is NOT programmer’s responsibility

More Tips…

int a[ ] = 30, 20, 16, 18, 35 ;for ( int i = 0 ; i <= 40 ; i++ )

System.out.println ( a[ i ] ) ; Exception

Instead of array of chars a type called string can be used

char str1[ ] = 'H', 'e', 'l', 'l', 'o' ;for ( int i = 0 ; i < str1.length ; i++ )

System.out.println ( str1[ i ] ) ;

String str2 = "Hello" ;System.out.println ( str2 ) ;

Variable Sized Arrays

int n = 4 ;int a[ ] = new int [ n ] ;

NoteDimension can be a variablen can be scanned through keyboard

HeapStacka

Array of Integers

11 3 6 9


Enterprise Solutions Using J2EE /

MoreArrays


Enterprise Solutions Using J2EE / Lecture 29

Objectives

Selection Sort Algorithm

Bubble Sort Algorithm

Reallocation of Arrays

Deallocation of Arrays

Passing Arrays elements / entire Array

Returning an Array


Selection Sort17 6 13 12 2 i6 17 13 12 26 17 13 12 26 17 13 12 22 17 13 12 62 2 2 2 6 2 6

2 6 12

13 17 12 612 17 13 66 17 13 12 1 - 4

13 17 1212 17 13

2 - 32 - 4

13 17 3 - 4

j0 - 10 - 20 - 30 - 41 - 21 - 3

public class SelectionSort


int a[ ] = 17, 6, 13, 12, 2 ;int i, j, t ;for ( i = 0 ; i <= 3 ; i++ )

for ( j = i + 1 ; j <= 4 ; j++ )

if ( a[ i ] > a[ j ] )

t = a[ i ] ; a[ i ] = a[ j ] ;a[ j ] = t ;

for ( i = 0 ; i <= 4 ; i++ )

System.out.println ( a[ i ] ) ;



13 17

Bubble Sort

17 6 13 12 2 i 6 17 13 12 2 0 - 1

1 - 22 - 33 - 4

6 13 17 12 26 13 12 17 26 13 12 2 17

6 13 12 2 0 - 16 12 13 2 6 12 2 136 12 26 2 12

2 6

1 - 22 - 30 - 11 - 2

12 13 17 0 - 1

i+1

17

13 17

17

17

public class BubbleSort


int a[ ] = 17, 6, 13, 12, 2 ;int i, j, t ;for ( j = 0 ; j <= 3 ; j++ )

for ( i = 0 ; i <= 3 - j ; i++ )

if ( a[ i ] > a[ i + 1 ] )

t = a[ i ] ; a[ i ] = a[ i + 1 ] ;a[ i + 1 ] = t ;

for ( i = 0 ; i <= 4 ; i++ )

System.out.println ( a[ i ] ) ;

13 17


Sorting Procedures

Selection SortBubble SortShell SortShuttle SortHeap SortMerge SortRadix SortQuick Sort

Fastest?

n2

log2n

For n = 10, Order = 3

For n = 10, Order = 100

Recursion


Reallocation & Deallocationint a[ ] = 1, 2, 3, 4, 5 ; int b[ ] ;System.out.println ( a ) ;b = a ;a = new int [ 10 ] ;for ( int i = 0 ; i <= 4 ; i++ )

a[ i ] = b[ i ] ;for ( int i = 5 ; i <= 9 ; i++ )

a[ i ] = 20 ;a = null ; System.out.println ( a[ 0 ] ) ;System.out.println ( b[ 0 ] ) ; 1

All arrays are dynamically allocatedArrays can be resized Arrays can be de-allocated during execution

Exception

f548743452



Heap

n Integers11 4 2 9

Stacka

ProblemCreate an array by receiving its size and its values

int n ;S.o.p ( "Enter Size" ) ; // receive nint[ ] a = new int [ n ] ;

Increase size of array by 3 elements, receive all elements again

a = new int [ n + 3 ] ;

for ( i = 0 ; i < a.length ; i++ )

// receive n a[ i ] = n ; S.o.p ( a[ i ] ) ;

Print the values

for ( i = 0 ; i < a.length ; i++ )

// receive n ;a[ i ] = n ;

n + 3 Integers5 4 6 1 0 7 9


Passing Array Elementsclass Array


int[ ] a = 7, 9, 16, -2, 8 ; int i ;display ( a[ 0 ], a[ 1 ], a[ 2 ], a[ 3 ], a[ 4 ] ) ;for ( i = 0 ; i < a.length ; i++ )

display1 ( a[ i ] ) ;static void display ( )

S.o.p ( i + " " + j + " " + k + " " + l + " " + m ) ;static void display1 ( )

S.o.p ( n ) ;

int i, int j, int k, int l, int m

int n

Whichis good?

102 106 110 114 118

a[0] a[1] a[2] a[3] a[4]8-21697


display ( b ) ;


int a[ ] = 7, 9, 16, -2, 8 ;

display ( a ) ;

class PassingArray

static void display ( )int [ ]p

int i ;for ( i = 0 ; i < p.length ; i ++ )

System.out.println ( p[ i ] ) ;

Passing Entire Array

102 106 110 114 118

a[0] a[1] a[2] a[3] a[4]8-21697

int b[ ] = 1, 3, 6, -2, 18, 1, 1, 7, 1, 1 ;





int p[ ] = fun( ) ;

class ReturningArray

public static int[ ] fun( )

for ( i = 0 ; i < p.length ; i ++ )

Returning An Array

102 106 110 114 118

a[0] a[1] a[2] a[3] a[4]8-21697

int a[ ] = 7, 9, 16, -2, 8 ;return ( a ) ;


Still More

ArraysYashavant [email protected]

Objectives

Passing array elements / array

Returning an array

Two-Dimensional Arrays

Initialization of 2D Array

Passing 2D Array

Returning 2D Array

Passing Array Elementsclass Array


int[ ] a = 7, 9, 16, -2, 8 ; int i ;display ( a[ 0 ], a[ 1 ], a[ 2 ], a[ 3 ], a[ 4 ] ) ;for ( i = 0 ; i < a.length ; i++ )

display1 ( a[ i ] ) ;static void display ( )

S.o.p ( i + " " + j + " " + k + " " + l + " " + m ) ;static void display1 ( )

S.o.p ( n ) ;

int i, int j, int k, int l, int m

int n

Whichis good?

102 106 110 114 118

a[0] a[1] a[2] a[3] a[4]8-21697


display ( b ) ;


int a[ ] = 7, 9, 16, -2, 8 ;

display ( a ) ;

class PassingArray

static void display ( )int [ ]p

int i ;for ( i = 0 ; i < p.length ; i++ )


Passing Entire Array

102 106 110 114 118

a[0] a[1] a[2] a[3] a[4]8-21697

int b[ ] = 1, 3, 6, -2, 18, 1, 1, 7, 1, 1 ;



int p[ ] = fun( ) ;

class ReturningArray

public static int[ ] fun( )

for ( i = 0 ; i < p.length ; i++ )

Returning An Array

102 106 110 114 118

a[0] a[1] a[2] a[3] a[4]8-21697

int a[ ] = 7, 9, 16, -2, 8 ;return ( a ) ;

S.o.p ( a[ ][ ] ) ;

2-D Arraypublic static void main( )

int a[ ][ ] = 2, 6, 1, 8, 4 1, 2, 5, 6, 8 7, 9, 8, 7, 21 4, 5, 6, 8, 10

;int i, j ;

2 4for ( i = 0 ; i < a.length ; i++ )

for ( j = 0 ; j < a[ i ].length ; j++ ) System.out.print ( a[ i ][ j ] + " " ) ;

System.out.println( ) ;

21

,

,,

compulsory

class Sample

compulsory


class Biggest public static void main( )

int a[ ][ ] =

7, 2, 6, 1 , 3, 5, 4, 8 , 6, 2, 9, 50

;

big = a[ 0 ][ 0 ] ; for ( i = 0 ; i < a.length ; i++ )

for ( j = 0 ; j < a[ i ].length ; j++ )

if ( > big )

big = a[ i ][ j ] ;

r = i ; c = j ;

S.o.p ( big ) ; S.o.p ( r + " " + c ) ;

r = 0 ; c = 0 ;int i, j, big ; int r, c ;

Find Biggest...

Find Second Biggestand its Position

a[ i ][ j ]

Initialisation of 2-D Arrays

int a[ ][ ] = new int [3][4] ; a[0][0] = 7 ; a[0][1] = 2 ; a[0][2] = 6 ; a[0][3] = 1 ; a[1][0] = 9 ; a[1][1] = 3 ; a[1][0] = 4 ; a[1][1] = 5 ; a[2][0] = 10 ; a[2][1] = 12 ; a[2][0] = 16 ; a[2][1] = 18 ;

9 3 4 5 10 12 16 181627402 418 434

int a[ ][ ] = 7, 2, 6, 1 , 9, 3, 4, 5 , 10, 12, 16, 18 ;

int [ ][ ]a = new int [3][4] ;

aStack

Row Major

Passing 2D Array

int a[ ][ ] = 1, 2, 3 , 4, 5, 6 ;int sum ;

public static int fun ( int b[ ][ ] )

int i, j ;for ( i = 0 ; i < b.length ; i++ )

for ( j = 0 ; j < b[ i ].length ; j++ )s = s + b[ i ][ j ] ;

return ( s ) ;

class TwoD


sum = fun ( a )S.o.p ( sum ) ; 21


S.o.p ( b[ 0 ][ 0 ] + " " + b[ 1 ][ 1 ] ) ;

Returning 2D Array

int b[ ][ ] ;

public static int [ ][ ] fun( )

int i, j ;for ( i = 0 ; i < b.length ; i++ )

for ( j = 0 ; j < b[ i ].length ; j++ )b[ i ][ j ] += 20 ;

return ( b ) ;

class TwoD


b = fun( ) ;

int b[ ][ ] = 1, 2, 3 , 4, 5, 6 ;


Types ofArrays


Objectives

3D Arrays

Array of References

Jagged Arrays

Passing Jagged Array

Returning Jagged Array

3D Jagged Array

Heap7 1 32 9 6

3D Arrays

aStack 4 5 1

1 3 89 2 2

1 4 32 7 8

1 4 3

int a[ ][ ][ ] = … ;S.o.p ( a[ 3 ][ 1 ][ 2 ] ) ;S.o.p ( a.length + " " + a[0].length + " " + a[0][1].length ) ;

4 2 3


Accessing

for ( int i = 0 ; i < a.length ; i++ )

for ( int j = 0 ; j < a[ i ].length ; j++ )

for ( int k = 0 ; k < a[ i ][ j ].length ; k++ )S.o.print ( a[ i ][ j ][ k ] ) ;

S.o.println( ) ;

for ( int arr2d[ ][ ] : a )

for ( int arr1d[ ] : arr2d )

for ( int item : arr1d )S.o.print ( item ) ;

S.o.println( ) ;

Or

Heap7 1 32 9 64 5 1

1 3 89 2 2

1 4 32 7 8

1 4 3

Array Of References

Heap

Array of Sample refs

Sample objects

Sample s[ ] ;s = new Sample [ 4 ] ;for ( int i = 0 ; i <= 4 ; i++ )

s[ i ] = new Sample( ) ;

sStack

Represent This...


Jagged Arrays

int a[ ][ ] = new int [3][ ] ;

a[0][0] = 7 ; a[0][1] = 2 ; a[0][2] = 6 ; a[0][3] = 1 ; a[1][0] = 9 ; a[1][1] = 3 ; a[1][2] = 4 ; a[2][0] = 1 ; a[2][1] = 8 ;

a[0] = new int [4] ;a[1] = new int [3] ;a[2] = new int [2] ;

for ( int i = 0 ; i < a.length ; i++ )

for ( int j = 0 ; j < a[ i ].length ; j++ )System.out.print ( a[ i ][ j ] ) ;

System.out.println( ) ;

HeapStacka

791

2 6 13 48

a - Ref. to arr of Ref.a[0] - Ref. to 1D arra[1] - Ref. to 1D arra[2] - Ref. to 1D arr

public class Jagged


int a[ ][ ] = new int [2][ ] ;a[0] = new int [4] ; a[1] = new int [3] ; a[0][0] = 7 ; a[0][1] = 2 ; a[0][2] = 6 ; a[0][3] = 1 ; a[1][0] = 9 ; a[1][1] = 3 ; a[1][2] = 4 ; int sum ;sum = fun ( a ) ; System.out.println ( sum ) ;

public static int fun ( int b[ ][ ] )

int i, j ; int s = 0 ;for ( i = 0 ; i < b.length ; i++ )

for ( j = 0 ; j < b[ i ].length ; j++ )s = s + b[ i ][ j ] ;

return s ;

Passing Jagged Arrays

HeapStacka 7

92 6 13 4

Returning Jag. Arr.public class JaggedArrays


int i, j ; int b[ ][ ] ;b = fun( ) ;for ( i = 0 ; i < b.length ; i++ )

for ( j = 0 ; j < b[ i ].length ; j++ )System.out.print ( b[ i ][ j ] ) ;

public static int[ ][ ] fun( )

int a[ ][ ] = new int [2][ ] ;a[0] = new int [4] ; a[1] = new int [3] ;a[0][0] = 7 ; a[0][1] = 2 ; a[0][2] = 6 ; a[0][3] = 1 ; a[1][0] = 9 ; a[1][1] = 3 ; a[1][2] = 4 ; return a ;

Heap

79

2 6 13 4


Heap

3D Jagged Array

1st 2D Arr - 2C, 4C, 3C0th 2D Arr - 3C, 5C

3D Jagged ArraysStack

arr 1 4 3

8 0 9

1 32 2 7 9 1

2 7 5 6

What isarrarr[ 0 ] arr[ 0 ][ 0 ]

int arr[ ][ ][ ] = new int[ 2 ][ ][ ] ;arr[ 0 ] = new int [ 2 ][ ] ;arr[ 1 ] = new int [ 3 ][ ] ;arr[ 0 ][ 0 ] = new int [ 3 ] ;arr[ 0 ][ 1 ] = new int [ 5 ] ;arr[ 1 ][ 0 ] = new int [ 2 ] ;arr[ 1 ][ 1 ] = new int [ 4 ] ;arr[ 1 ][ 2 ] = new int [ 3 ] ;


Using NetBeans Effectively


ObjectivesWhat are Edit HintsHow to NavigateWhat is Code completion featureWhat is code RefactoringHow to achieve Refactoring in NetBeans

Creating New Project


NetBeans ViewsProjects View

Add New Class

R

Utility.java – Add throws


Utility.java

Edit Hints – try-catch





Edit Hints 2 – import


Edit Hints 2 – import

Navigation – Ctrl + Mouse

Navigation – Ctrl + Mouse


Code Completion – Step 1

After typing . complete list appears

Code Completion – Step 2

Code Completion - Result


Code Completion – Multiple

Ctrl + Spacebar

Refactoring - Rename

R


R


Configure – Tools | Options

Configure – Tools | Options

Code Templates


Bitwise OperatorsYashavant [email protected]

Objectives

Need for using Bitwise operatorsOne's complement operatorBitwise &, |, ^ operatorsBitwise <<, >>, >>> operators

Binary to Hex. is convenient

Binary - 0..1 Octal - 0..7Decimal - 0..9 Hexadecimal - 0...9, A...F

Binary to decimal is inconvenient

Bits etc.

Numbering systems

- 0xFA

- 0x76

Bit - Binary Digit - Basic unit of informationCan take a value 0 or 14 bits = Nibble 8 bits = Byte16 bits = Word 32 bits = DWord

1000 81001 91010 A1011 B1100 C1101 D1110 E1111 F

0000 00001 10010 20011 30100 40101 50110 60111 7

0111 01101111 1010

0111 01101111 1010

- 2+4+16+32+64

- 2+8+16+32+64+128


Need For Bitwise Operators

int ch = 32 ;

01234567152331

check 1 or 0 set to 0 or 1

One's Complement Operator

int ch = 32 ;S.o.print ( ~ch ) ;

111111111111111111111111111011111

-11111111111111111111111111011110

~

00000000000000000000000000100000~

11111111111111111111111111011111 -ve

00000000000000000000000000100001

-33

-33

Original

And, Or, Xor

& 0 10 0 01 0 1

| 0 10 0 11 1 1

^ 0 10 0 11 1 0

0000000000000000000000000010000111111111111111111111111111100001&

00000000000000000000000000100001

|

1111111111111111111111111100001

11111111111111111111111111000000

^

Mask

New

0000000000000000000000000010000111111111111111111111111111100001

0000000000000000000000000010000111111111111111111111111111100001


if ( )

Utility of & and I7 6 5 4 2 1 0

& 0 0 0 0 1 0 0 00 0 0 0 0 0 00/1

3

1- - - - - - -1 1 1 1 0 1 1 1- - - - - - -0

S.o.println ( "Enter a no." ) ;// receive n = byte.ParseByte( )

byte n ;

n & 8 == 8

S.o.p ( n ) ;else

S.o.p ( "3rd bit is off" ) ;n = n | 8 ;

n0/1- - - - - - -

n = n & 0xF7 ;

&

S.o.p ( "3rd bit is on" ) ;

& 0 10 0 01 0 1

Utility of &Check whether a bit is on or offPut off a particular bit

0- - - - - - -0 0 0 0 1 0 0 0- - - - - - -1

|

Utility of | Put on a bit

Bitwise CA oper.&= |= ^= <<= >>=

n |= 8 ;

Right Shift >>

int ch = 32 ;System.out.print ( ch >> 2 ) ;System.out.print ( ch ) ;

>> 2

8

32

ch >> 1 Divides by 2, discards remainderSign is not changed

00000000000000000000000000100000

000000000000000000000000001000- -00

System.out.print ( 35 >> 2 ) ; 8

Left Shift <<

int ch = 32 ;System.out.print ( ch << 1 ) ;System.out.print ( ch ) ;

<< 1

32

ch << 1 Multiplies by 2,if 1’s are not lostSign is not changedSign may change

00000000000000000000000000100000

0000000000000000000000000100000-0

<< 2

01000000

00000000

<< 1

01000000

100000001 is lost Sign is changed

64


Unsigned Shift

int ch = -1 ;System.out.print ( ch >> 1 ) ;System.out.print ( ch >>> 1 ) ;

>> 1

2147483647

>>> Should be used only with int or long intbyte and short are anyway promoted to ints

1111111111111111111111111111111

1111111111111111111111111111111-

System.out.print ( ch ) ;

0111111111111111111111111111111-

-1SignExtended

>>> 1

-1

10011 0001 0011000

Binary

Utility Of <<, >>

( 1999 - 1980 ) * 5121 * 32+

+ 69766

= 9728= 32= 6

yr m d

7 Bits 4 Bits 5 Bits

For every file, Date and Time are stored as two-byte entries

m s

6 Bits 5 Bits5 Bits

hr

1 + 2 + 16 + 1980 = 1999 1 2 + 4 = 6

d, m, y

class Date

public static void main ( .. )

int dt = 9766 ;short d, m, y ;y = ( short ) ( ( dt >> 9 ) + 1980 ) ;m = ( short ) ( ( dt << 23 ) >> 28 ) ;d = ( short ) ( ( dt << 27 ) >> 27 ) ;S.o.println ( d + " " + m + " " + y ) ;

6 1 1999

00000000 00000000 0010011 0001 00110>> 9

00000000 00000000 0010011000000000

00000000 00000000 0010011 0001 00110

m d

4 5

1

InheritanceYashavant [email protected]

Objectives

Cornerstones of OOP

Reuse Mechanisms

What is Containership

What is Inheritance

Object sizes in Inheritance

OO Programming

Encapsulation

Inheritance

Polymorphism

- Hides complexity

- Promotes reuse

- Generalizes actions

Facilitated by Classes and Objects

2

Reuse Mechanisms

Containership Inheritance

Window

Button

StringList

String

"Has a" relationship

"Like a" relationship

Non-OO Lang. - Has aOO Lang. - Has a, Like a

Vehicle

Combination of Relationships

Engine

Vehicle

Car

Car

EngineWhat do you see?

Main W, Project W, Error W, Program WDifferent things in different WindowsBut each specific W is still Like a window

Where are they?All W are contained inside Main Window

Window

Error W Pro Win

Main WindowPro. W.Error W.

O/P W. Prog. W

private int count ;

Index i = new Index ( );

Inheritanceclass Index

count -= 1 ;

class Program

public static void main( .. )

class index1 extends Index

public void decr( )

0

1

0

i.incr( ) ;

i.decr( ) ;

public void display( )

S.o.p ( count ) ;public void incr( )

count += 1 ;

i.display( ) ;

i.display( ) ;

public Index( )

count = 0 ;

protected int count ;

i.display( ) ;

Index1 i = new Index1( ) ;

display( ), incr( ) - Not part of index1

3

class Index

private

protected

public

private

protected

public

Index1 i = new Index1( ) ;

Access

class Index1 extends Index

Index j = new Index( ) ;

All Casesclass base

private

protected

public

private

protected

public

class der extends base

class Myclass

base b ;

derived d ;

base b ;der d ;

Object Sizesclass base1

private int i ;protected int j ;public int k ;

class derv extends base1

private int x ;protected int y ;public int z ;

base1 b = new base1( ) ;derv d = new derv( ) ;

final - Shared by defaultstatic - Is never a part of object

i kj

b

i kj x y z

d

4

Inheritance in real life

Simple mindedGood English oratorToo religious

Simple mindedGood English oratorModerately religiousGood English writing skills

Simple mindedGood English and Hindi oratorScorn for religionGood sportsman

- As it is- As it is- Change

- New

- As it is- Combination

- Change- New


More InheritanceYashavant Kanetkar

[email protected]

ObjectivesWhat does Inheritance offer us

Practical application of Inheritance

How objects are constructed in Inheritance chain

How to prevent Inheritance

Calls...

S.o.p ( "b.f2" ) ;

public void f3( )

S.o.p ( "b.f3" ) ;public void f4( )

S.o.p ( "b.f4" ) ;

class a

class b extends a

super.f2( ) ;

public void f2( )z.f4( ) ;

Cases

Use ExistingOverrideNew Combinationpublic void f1( )

S.o.p ( "a.f1" ) ;

public void f2( )

S.o.p ( "a.f2" ) ;

class Sample


b z = new b( ) ;z.f1( ) ;z.f2( ) ;z.f3( ) ;

a.f1b.f2b.f3

a.f2 b.f4


A Practical ScenarioA company has created software which has several classesAfter a market survey before the next version following requirements have to be met:

A new Auto Update feature should be addedBug was discovered while saving files > 400 kb

Data encryption function is too slowWhile opening a file opening progress should be displayedRest of the functionality is acceptable

New - autoupdate( )Change - save( ), encrypt( )Combination - open( )Use Existing - fun( )

Implementation

public void enc( ) S.o.p ( "Encrypt" ) ;

public void autoupdate( )

S.o.p ( "AU" ) ;

public void save( )

S.o.p ( "Save" ) ;

public void open( )

S.o.p ( "Open" ) ;

news x = new news ( ) ;

public void open( ) // progress barsuper.open( ) ;

class s

public void save( ) // fix bug

class news extends s

x.fun( ) ;x.autoupdate( ) ;

x.save( ) ;

public void fun( )

S.o.p ( "fun" ) ;

public void enc( )

S.o.p ( "Encrypt" ) ;

x.enc( );x.open( ) ;

Ctor Calls

class b extends a

b( )

S.o.p ( "b's 0-arg Ctor" ) ;

class a

a( )

S.o.p ( "a's 0-arg Ctor" ) ;a ( int xx )

S.o.p ( "a's 1-arg Ctor" ) ;

class Myclass


b y = new b( ) ; b z = new b ( 10 ) ;

a’s 0-arg Ctor

b’s 0-arg Ctora’s 1-arg Ctorb’s 1-arg Ctor

b ( int x )

super ( x ) ;s.o.p ( "b's 1-arg Ctor" ) ;

Call to super must be 1st statementIf super( ) is absent a's 0-arg Ctor is calledsuper can also be used to call base class fun.


Why Base To Derivedclass base

protected int i ;public base( )

i = 4 ;


int j ;public der( )

j = i * 4 ;

class Program


der d = new der( ) ;

Construction always proceedsfrom base towards derived

Conflict...

class derived extends base

int i = 9 ;

class base

protected int i = 13 ;…

public void fun( )

System.out.println ( i + " " + super.i ) ;

9 13

class shape

final void draw( )

S.o.p ( "shape" ) ;

class circle extends shape

void draw( )

S.o.p ( "circle" ) ;

Error

final class shape

void draw( )

S.o.p ( "shape" ) ;

class circle extends shape

void draw( )

S.o.p ( "circle" ) ;

Error

final fun. can’t be overriddenfinal class cannot be inherited

Prevent Inheritance


Inheritance SummaryBase class - Super class, Parent classDerived class - Sub class, Child classDerived class object contains all base class dataDer. class obj. may not be able to access all base class dataIn inheritance chain construction happens from B to DInheritance facilitates - Inherit, Suppress, ExtendInherit - Do nothingSuppress - Hide base class implementationExtend - super.Baseclassmethod( )final - Prevent inheritance


Exception Handling - IYashavant Kanetkar

[email protected]

ObjectivesWhen things may go wrongWhat can go wrong during executionTypes of ExceptionsWays to tackle Exceptional ConditionDifference between Checked & UncheckedHow to tackle Checked Exceptions

Wishful Thinking

I am a good Programmer

Everything isgoing to go well

"My" program would anyway work correctly


Examples

When Things May Go Wrong

Short of memoryDivide by zeroExceeding the bounds of an arrayStack overflowArithmetic over flow or under flowAttempt to use an unassigned referenceFile not foundUnable to connect to Server

Reported by - CompilerAction - Debug program

Reported by - LinkerAction - Proper imports

Reported by - Java RuntimeAction - Tackle it on the fly

During Compilation

During Linking

During Execution

What Can Go Wrong During Execution

Occurrence of Exceptional Condition

Due to Internal Cond.

Due to External Cond.

Can be anticipated

Recovery possible

Can't be anticipated

Recovery Impossible

File not found Insufficient memory

Passing null instead of filename

Disk failure while reading

k/a Checked Exceptions

k/a Runtime Exceptions k/a Errors

Tackling Exceptional Condition• Exceptional conditions occur during method execution• All Exceptional Conditions are tackled in OO manner• Info @ exceptional condition is packed into an object• Java provides a class hierarchy to represent Exc. cond.

Object

Throwable

Error Exception

RuntimeException...

...

...

External Unchecked

Internal Unchecked

Checked Cond.


Tackling Checked ExceptionsMethod called from client code is executing

Exceptional Condition occurs

Pack exception info. in an object

Let Java Runtime pack exception info. in an object

Throw the object

Do nothing Catch the object in client code

Rectify & continue Graceful exitDefault exception handlerCatches the object

Prints Stack Trace& terminates

Case 3Case 2

Case 1

import java.io.* ;public class Case1


int i ;BufferedReader b ;b = new BufferedReader ( new InputStreamReader (

System.in ) ) ;System.out.println ( "Enter a number: " ) ;i = Integer.parseInt ( b.readLine( ) ) ;

Case 1: Do Nothing

Exception in thread "main" java.lang.NumberFormatException: For input string: "abc"

at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)at java.lang.Integer.parseInt(Integer.java:447)at java.lang.Integer.parseInt(Integer.java:497)at Sample.Case1.main(Case1.java:24)

ClumsyBad practice

Why?

Case 2: Recover & Cont.import java.io.* ;public class Case2

public static void main (String[ ] args ) throws Exception

int i ;BufferedReader b ;b = new BufferedReader (

new InputStreamReader ( System.in ) ) ;while ( true )

try

System.out.println ( "Enter a number: " ) ;i = Integer.parseInt ( b.readLine( ) ) ;break ;

catch ( NumberFormatException e )

System.out.println ( "Incorrect Input" ) ;

System.out.println ( "You entered: " + i ) ;

Hope for the best, prepare for the worst policy


Case 3: Graceful Exitimport java.io.* ;public class Case3

public static void main ( String[ ] args) throws Exception

int i ;BufferedReader b ;b = new BufferedReader ( new

InputStreamReader ( System.in ) ) ;try

System.out.println("Enter a number: ");i = Integer.parseInt ( b.readLine( ) ) ;System.out.println ( "You entered: " + i ) ;

catch ( NumberFormatException e )

System.out.println ( "Incorrect Input." ) ;


Exception Handling - IIYashavant Kanetkar

[email protected]

ObjectivesA quick recap...How to catch multiple exceptionsHow finally block worksWhat is the purpose of the finally blockHow to tackle unchecked exceptionsNested try statements

Recap...Exceptions are treated as objectsChecked & Unchecked Exceptions3 choices When an exception occurs

Do nothing, Rectify and continue, Graceful exitEnclose code where you anticipate error in try blockCatch the thrown exception in catch blockcatch block must immediately follow the try blockWhen exception is thrown, control goes to catch blockAfter catch block is executed, control goes to the next line after catch block(s) unless there is a return or throw in the catch blockOn calling a method that has advertised that it will throw an excep., you have to either catch or rethrow


Catching Multiple Exceptionsimport java.io.* ;import java.lang.* ;public class MultipleExceptions


int i, j ;BufferedReader b = new BufferedReader (

new InputStreamReader ( System.in ) ) ;try

S.o.p ( "Enter i: " ) ;i = Integer.parseInt ( b.readLine( ) ) ;S.o.p ( "Enter j: ");j = Integer.parseInt ( b.readLine( ) ) ;S.o.p ( "You entered: %d, %d\n", i, j ) ;S.o.p ( "Result: %d\n", i / j ) ;

Contd...

catch ( NumberFormatException ne )

S.o.p ( "Incorrect Input." ) ; catch ( ArithmeticException ae )

S.o.p ( "Arithmetic Exc. / by zero." ) ; catch ( Exception e)

S.o.p ( "Unknown Error: " + e ) ;

...Contd.

Multiple catch blocks are OKAt a time only one catch block goes to work Order of catch blocks is important - Derived to Base

import java.io.*;import java.lang.*;public class Case5


FileWriter fw = null ;try

fw = new FileWriter ( "a.txt" ) ;fw.write ( "Hello World\n" ) ;

catch ( IOException ie )

S.o.p ( "Encountered IO Error" ) ; finally

finally Block

Contd...


if ( fw != null )

try

fw.close( ) ; catch ( IOException ex )

S.o.p ( "Cannot close file" ) ;

...Contd.

Code in finally always runs, no matter what!Even if a return or break occurs firstException: System.exit( )

Placed after catch blocks (if they exist)try block must have catch block and/or finally blockfinally clause is optional

Not checked at compilation timeThese are never advertised by methodsTwo types:

Tackling Unchecked Exceptions

Error or its Subclasses

Don't catchYou don't know what to do

- Use Checked exceptions for recoverable conditions - Use Runtime exceptions for programming errors

Runtime or its Subclasses

Ex. Internal Error

Ex. VM Error

Shouldn't happen, Fixed while testingSimilar to Assert( ) macro

Ex. Division by 0

Ex. Improper array index

A try statement can be inside the block of another tryEach time control enters a try, the context of that exception is pushed on the stackIf inner try doesn't have a catch, then the outer try'scatch handlers are inspected for a matchIf method called from a try block has try block withinit, then then it is also nested try

Nested Try Statements


User-defined ExceptionsYashavant Kanetkar

[email protected]

ObjectivesWhat are user-defined exceptionsWhen do we need to create themHow to create them – ExamplesException etiquettes

User-defined ExceptionsException

Customer

Name Acc No. Bal.

withdraw( )

getbalance( )

myexcep

myexcep( )

message( )

ClientWhile withdrawing, if balance goes below

Rs. 500, throw an exception


import java.io.* ;public class Customer

private String name ;private int accno ;private int balance ;

public Customer ( String n, int a, int b )

name = n ; accno = a ; balance = b ;public void withdraw ( int amt ) throws BankException

if ( balance - amt <= 500 )throw new BankException ( accno, balance ) ;

balance -= amt ;

Customer Class

Means Need has arisen, so throw

Means If needed would throwIf not, won't throw

public class Client


Customer c = new Customer ( "Rahul", 2453, 900 ) ;try

c.withdraw ( 450 ) ; catch ( BankException ex )

System.out.println ( "Transaction failed" ) ;ex.inform( ) ;

Client Class

class BankException extends Exception

private int acc ;private int bal ;public BankException ( int a , int b)

acc = a ;bal = b ;

public void inform( )

System.out.printf ( "Acc. No.: %d\n", acc ) ;System.out.printf ( "Balance: %d\n", bal ) ;

BankException Class


Exception

Stack

One More Example

push( )pop( )

getSize( )

data[ ]capacity

size

StackException

StackException( )

StackException ( String )

VinodSanjay

353.14

main( )

Create Stack object

push elements

pop elements

package stacktest ;class StackTest


Stack s = new Stack ( 3 ) ;try

s.push ( "Vinod" ) ;s.push ( "Sanjay" ) ;s.push ( new Integer ( 25 ) ) ;s.push ( new Float ( 3.14f ) ) ;

catch ( StackException x )

S.o.p ( x ) ;

try

while ( s.getSize( ) > 0 )S.o.p ( s.pop( ) ) ;

catch ( StackException x )

S.o.p ( x ) ;

StackTest Class

class Stack

private int capacity ;private int size ;private Object[ ] data ;

public Stack ( int cap )

data = new Object [ cap ] ;capacity = cap ; size = 0 ;

public void push ( Object o ) throws StackException

if ( size == capacity )throw new StackException ( "Stack full" ) ;

data[ size++ ] = o ;

Stack Class

Contd...


public Object pop( ) throws StackException

if ( size <= 0 )throw new StackException ( "Stack empty" ) ;

return data [ --size ] ;

public int getSize( )

return size ;

...Contd.

class StackException extends Exception

StackException( )

StackException ( String msg )

super ( msg ) ;

StackException Class

Exception EtiquetteSet val. in a public static var. (like global) in some classReturn a boolean, int, string or an object from a methodDon’t catch & ignore

Don't use exception handling for cosmetic purposeDon't catch everything using ExceptionAlways try to distinguish between types of exceptionsMake it optimally elaborate – not too much, not too little

catch ( Exception e )


Abstract ClassesYashavant Kanetkar

[email protected]

Objectives

♦ What is dynamic despatch mechanism

♦ What are abstract classes

♦ How to construct abstract classes & methods

♦ Example programs to demonstrate abstract Classes

♦ What can be / cannot be done using abstract classes

class Shape

void Draw( ) class Circle extends Shape

void Draw( )

S.o.p ( "Circle" ) ;

class Rect extends Shape

void Draw( )

S.o.p ( "Rectangle" ) ;

public class Myclass


Circle c1, c2, c3 ;c1 = new Circle( ) ;...rect r1, r2, r3 ;r1 = new Rect( ) ;...Shape s[ ] = c1, r2, … ;for ( int i = 0 ; i <= 5 ; i++ )

s[ i ].Draw( ) ;

Dynamic Dispatch Mechanism

Calls suitabledraw( )How to prevent creation of Shape objects


Example I

PrinterCtor( )print( )

String name

LaserPrinter

Ctor( )print( )

InkjetPrinter

Ctor( )print( )

♦ Every printer uses its own way to print♦ Application should be able to print to any printer♦ Application need to know only name of the printer to print♦ To do the printing application should merely call print( )

Abstract class

Derived classes

Usagepackage abstractdemo ;import java.io.* ;public class AbstractDemo


Printer p = new LaserPrinter ( "LaserJet 1100" ) ;p.print ( "hello1.pdf" ) ; p = new InkjetPrinter ( "IBM 2140" ) ;p.print ( "hello2.doc" ) ;

Abstract Classabstract class Printer

protected String name ;public Printer ( String n )

name = n ;public abstract void print ( String docName ) ;

♦ Object cannot be created from abstract class♦ An abstract class can contain abstract & non-abstract fun.♦ Abstract class may contain instance & static variables♦ These variables may be inherited♦ Abstract methods do not have a body♦ Abstract classes can participate in inheritance♦ If a class contains abstract methods class has to be abstract

Partial Implementation


class LaserPrinter extends Printer

public LaserPrinter ( String n ) super ( n ) ; public void print ( String docName )

System.out.println ( " >> LaserPrinter.print" ) ;

class InkjetPrinter extends Printer

public InkjetPrinter ( String n ) super ( n ) ; public void print ( String docName )

System.out.println ( " >> InkjetPrinter.print" ) ;

Derived Classes

Example II

Image

filename

GIFImage

Ctor( )Load( )

JPEGImage

Ctor( )Load( )

♦ Each image format is different♦ Design classes to load / save different images♦ It should be possible to extend design to accommodate

new images in future

Create( )setImage( )

Load( )Save( )

Usagepackage abstractimagedemo ;import java.io.* ;

public class AbstractImageDemo


Image i = Image.Create ( "test.jpg" ) ;i.Load( ) ;i = Image.Create ( "test.gif" ) ;i.Load( ) ;

Class factory function

Creates appropriate object based on extension

Upcasting

Dyn. dispacth


Abstract Classabstract class Image

protected String fileName ;public void setImage ( String f )

this.fileName = f ;public static Image Create ( String f )

if ( f.toLowerCase( ).endsWith ( ".jpg" ) ) return new JPEGImage ( f ) ;

else if ( f.toLowerCase( ).endsWith ( ".gif" ) ) return new GIFImage ( f ) ;

return null ;

Contd...

public void Save ( char[ ] buf ) throws IOException

FileWriter fw = new FileWriter ( fileName ) ;fw.write ( buf ) ;fw.close( ) ;

public abstract void Load( ) ;

...Contd. Need not be abstract

How to save is same for any image

Should be abstract

Each type of image is loaded differently

Derived Classesclass JPEGImage extends Image

public JPEGImage ( String f ) setImage ( f ) ;

public void Load( )

System.out.println ( " >> JPEGImage.Load" ) ;

class GIFImage extends Image

public GIFImage ( String f ) setImage ( f ) ;

public void Load( )

System.out.println ( " >> GIFImage.Load" ) ;


InterfacesYashavant [email protected]

Objectives

♦ What are interfaces♦ How are they different than abstract classes♦ In which different situations can we use interfaces♦ Sample programs to demonstrate the situations

What Are Interfaces♦ Collections of functions declarations♦ Fun. are defined in classes that implement the int.

interface Mouse

void lbtndn ( Point p ) ;void rbtndn ( Point p ) ;

class GeniusM implements Mouse

public void lbtndn ( Point p )

S.o.p ( "Left Button" ) ;public void rbtndn ( Point p )

S.o.p ( "Right Button" ) ;

♦ Different classes may implement the same interface♦ A class can implement any number of interfaces

Keyword

What a class must do

How to do it


Interfaces V/s Abstract Classes

♦ Abstract class functions may have a body ♦ Interface functions never have a body♦ Abstract class may contain instance variables

♦ These variables may be inherited♦ Interface may contain variables

♦ These variables can be accessed♦ These variables are by default static and final

Interface ScenariosI. Permit focused view of a large implementation

Encrypt( )Decrypt( )

Compress( )Decompress( )

Authorize( )Authenticate( )

II. Provide different implementation of same tasks

III. Inherit desired qualities from unrelated sources

Count( ), Insert( )Add( ), Remove( )

ArrayCount( ), Insert( )Add( ), Remove( )

Linked List

♦ I want looks of John Abraham♦ I want character of Dr. Kalam

♦ I only want character of Dr. Kalam

I. Different Implementationpackage diffimpl ;import java.io.* ;public class DiffImpl


IListMethods i ;i = new MyArray( ) ;i.Add ( 1 ) ; i.Remove ( 1 ) ; i.Count( ) ;i = new MyLL( ) ;i.Add ( 1 ) ; i.Remove ( 1 ) ; i.Count( ) ;

1/4


Interface

interface IListMethods

public int Count( ) ;public void Add ( Object o ) ;public void Remove ( Object o ) ;

2/4

Array Implementationclass MyArray implements IListMethods

public int Count( )

System.out.println ( " >> MyArray.Count" ) ;return 0 ;

public void Add ( Object o )

System.out.println ( " >> MyArray.Add" ) ;public void Remove ( Object o )

System.out.println ( " >> MyArray.Remove" ) ;

3/4

Linked List Implementationclass MyLL implements IListMethods

public int Count( )

System.out.println ( " >> MyLL.Count" ) ;return 0 ;

public void Add ( Object o )

System.out.println ( " >> MyLL.Add" ) ;public void Remove ( Object o )

System.out.println ( " >> MyLL.Remove" ) ;

4/4


II. Focussed Viewpublic class InterfaceDemo


FocussedView o = new FocussedView( ) ;IEncrypt ie = o ;ie.Encrypt( ) ;ie.Decrypt( ) ; ICompress ic = o ;ic.Compress( ) ;ic.Decompress( ) ;IAuth ia = o ;ia.Login( ) ;ia.Logout( ) ;// ia.Compress( ) ; compiler error

1/3

Interfacespackage ooconcepts ;import java.io.* ;interface IEncrypt

public void Encrypt( ) ;public void Decrypt( ) ;

interface ICompress

public void Compress( ) ;public void Decompress( ) ;

interface IAuth

public void Login( ) ;public void Logout( ) ;

2/3

Implementationpublic class FocussedView

implements IEncrypt, ICompress, IAuth

public void Encrypt( )

S.o.p ( " >> Encrypt" ) ;public void Decrypt( )

S.o.p ( " >> Decrypt" ) ;public void Compress( )

S.o.p ( " >> Compress" ) ;

public void Decompress( )

S.o.p ( " >> Decomp." ) ;public void Login( )

S.o.p ( " >> Login" ) ;public void Logout( )

S.o.p ( " >> Logout" ) ;

3/3


III. Qualitiespackage ooconcepts ;import java.io.* ;public class Qualities


Model m ;Actor myself ;myself = new Actor( ) ;m = myself ; m.style( ) ; ICharacter ch ;ch = myself ;ch.patriotism( ) ;

1/3

Interface & Model Class

interface ICharacter

public void patriotism( ) ;

class Model

protected String hairstyle ;public void style( )

System.out.println ( ">> Model.style" ) ;

2/3

Actor Classclass Actor extends Model implements ICharacter

public void doActing( )

System.out.println ( ">> Actor.doActing" ) ;public void style( )

super.style( ) ;System.out.println ( ">> Actor.style" ) ;

public void patriotism( )

System.out.println ( ">> Character.patriotism" ) ;

3/3


Interfaces IIYashavant Kanetkar

[email protected]

Objectives

♦ Interface recap...♦ Bow and Arrow - Class Design♦ Bow and Arrow - Program

Recap...♦ Interfaces are not derived from Object class♦ Interfaces are not derived from any base interface♦ Interfaces contains only method declarations♦ Interfaces may contain static and final data♦ Objects cannot be created from interfaces♦ A class can implement multiple interfaces♦ Interfaces can be inherited♦ Multiple interface inheritance is allowed♦ Class cannot implement an interface partially♦ Interface can be used in three situations:

♦ Focused view♦ Different implementation of same task♦ Alternative for multiple inheritance


Bow & Arrow

Set steps for Shooter and BalloonsMake movement for Shooter and Balloons

Classes

Bow & Arrow

Shooter TimerBalloon

setstep( )move( )

setstep( )move( )

TargetTimerPerson

Possible Solution

Shooter s1 = new Shooter( ) ;Balloon b1 = new Balloon( ) ;Balloon b2 = new Balloon( ) ;Timer t [ ] = s1, b1, b2 ;

for ( int i = 0 ; i < 3 ; i++ )t [ i ] . setstep ( r . nextInt ( 5 ) ) ;

for ( int i = 0 ; i < 3 ; i++ )t [ i ] . move( ) ;

Random r = new Random( ) ;

Problems :

Unnatural relationshipNo Multiple Inheritance

Shooter Balloon


Correct Solution

TargetITimerPerson

Shooter BalloonImplement

Timer Interfaceinterface ITimer

void setstep ( int n ) ;void move( ) ;

class Shooter extends Person implements ITimer

private int step ;public void setstep ( int s )

step = s ;

public void move( )

S.o.p ( "Shooter moved: " + step ) ;step++ ;

Shooter Class


class Balloon extends Target implements ITimer

private int step ;public void setstep ( int s )

step = s ;

public void move( )

S.o.p ( "Balloon moved: " + step ) ;step++ ;

Balloon Class

public class BowAndArrow

static public void main ( String args[ ] )

Shooter s1 = new Shooter( ) ;Balloon b1 = new Balloon( ) ;Balloon b2 = new Balloon( ) ;ITimer t [ ] = s1, b1, b2 ;Random r = new Random( ) ;for ( int i = 0 ; i < 3 ; i++ )

t [ i ] . setstep ( r . nextInt ( 5 ) ) ;for ( int i = 0 ; i < 3 ; i++ )

t [ i ] . move( ) ;

BowAndArrow Class


Packages - IYashavant Kanetkar

[email protected]

Objectives♦ Anatomy of a NetBeans Project♦ What are packages♦ What do we gain from using packages♦ How to create packages and use them

Anotomy Of A NetBeans Project

C:\Users\Kanetkar\JavaPrograms\J43C:\Documents and Settings\Kanetkar\JavaPrograms\J43

Vista

Project NamePath

XP


Project Contents

.java Files .class Files .jar + javadoc Files

ant Script (build-impl.xml)

For customizing ant Script

Test classes

Version info

NetBeans ViewsProject View Files View

Package PkgWhat Are Packages

Package acts as a container for related typesPackage provides access protectionPackage makes is easy to locate and use typesPackage helps in avoiding naming conflicts

fun1( )fun2( )

var1var2

fun3( )fun4( )

var3var4

Class A Class B Enumeration

fun5( ) ;

Interface I

fun6( ) ;

fun7( ) ;Annotation


What Do We Gain

Intuitive indication for everyone that these types are relatedIndication of where to find graphics-related functions. Package creates a new namespace Helps avoid conflict of type-names with names in other pkgTypes in the pkg have unrestricted access to one anotherYet lets restrict access to types outside the package

Package Graphics

class Rectangle

class Freehand

class Spline

class Circle

package simpleinterest ;public class SimpleInterest

public float calculateSi ( float p, int n, float r )

float si ;si = p * n * r / 100 ;return ( si ) ;

Package Declaration

To access a type outside the package it should be public

A file can have only one public type in itNames of .java file and public type in it should be same

Must be first line Only 1 package stat. per file

Applies to all types in this file

Package Usage 1/3


2/3

3/3

C:\Documents and Settings\kanetkar\JavaPrograms\J43\src\j43C:\Documents and Settings\kanetkar\JavaPrograms\J43\src\sample

Result

Sample.java

public class Sample

public void show( )

S.o.p ( "Hello" ) ;

Client.java

public class Client


Sample a = new Sample( ) ;

package sample ; package client ;import sample.Sample ;

a.show( ) ;

If import is not done, use fully qualified name sample.Sample a = new sample.Sample( ) ;


Package FAQs

How do I ensure uniquenessUse reversed Internet domain name com.ksetindia.simpleinterestcom.ksetindia.quest

What if package name is absent?All types in the file belong to default package

Should package name be in small case?Good idea. Used by NetBeansAvoids name conflict with class / interface names

Pkgs in the Java language itself begin with java. or javax.

what if there is a name conflict within the companyEvolve a convention to resolve it

What if there is a hyphen in domain namereplace it with underscorecom.google-ads com.google_ads


Packages - IIYashavant Kanetkar

[email protected]

Objectives♦ What are split packages♦ How to access types in multiple packages♦ How to create and use nested packages♦ Access control mechanisms

public class Sample1

public void show( )

S.o.p ( "Hello" ) ;

package sample ;public class Sample2


S.o.p ( "Hi" ) ;

package sample ;

Split Package

C:\Docume~1\kanetkar\JavaPrograms\J44\src\sample\sample1.javaC:\Docume~1\kanetkar\JavaPrograms\J44\src\sample\sample2.java

C:\Docume~1\......................\J44\build\classes\sample\sample1.classC:\Docume~1\......................\J44\build\classes\sample\sample2.class

File | New File, Type and Save


Using Split Package

class Client


Sample1 s1 = new Sample1( ) ;

import sample.Sample2 ;import sample.Sample1 ;

Sample2 s2 = new Sample2( ) ;s1.show( ) ;

s2.display( ) ;

package j44 ;

A package can be split over multiple filesEach file can contain only one public type

import sample.*

* means import all public types present in sample package

Multiple Packages

public class Sample

public void show( )

S.o.p ( "Hello" ) ;

package sample1 ;public class Sample


S.o.p ( 'Hi" ) ;

package sample2 ;

C:\Docume~1\kanetkar\JavaPrograms\J45\src\sample1\sample.javaC:\Docume~1\kanetkar\JavaPrograms\J45\src\sample2\sample.java

C:\Docume~1\......................\J45\build\classes\sample1\sample.classC:\Docume~1\......................\J45\build\classes\sample2\sample.class

File | New File, Type and Save

Using Multiple Packages

class Client


sample1.Sample s1 = new sample1.Sample( ) ;

import sample2.Sample ;import sample1.Sample ;

sample2.Sample s2 = new sample2.Sample( ) ;s1.show( ) ;

s2.display( ) ;

package J45 ;import sample1.* ;import sample2.* ;

Can be deleted as we are using fully qualified names

True in all cases


Nested Packages

public class Sample

public void show( )

S.o.p ( "Hello" ) ;

package sample ;public class Trial


S.o.p ( "Hi" ) ;

package sample.trial ;

Using Nested Packages

class Client


Sample s = new Sample( ) ;

import sample.trial.Trial ;import sample.Sample ;

Trial e = new Trial( ) ;s.show( ) ;

e.display( ) ;

import sample.*

import FAQs

Are the following set of statements same

Which packages are imported by default?default package, java.lang, current package

Which packages would get imported by import graphics.A*;None. Compilation error.

Import all public types from dir C:\.....\example\ex1Import all public types from dir C:\.....\example\ex2\ex3

What do the following import statements mean? import example.ex1.* ;import example.ex2.ex3.* ;

import java.awt.shape.*import java.awt.color.* import java.awt. *

If a class is present in 2 packages will the code compileYes. Till we don't start using it


Same Package's Classpackage p1 ;public class First

staticpublic void main ( .. )

Myclass m = new Myclass( ) ;S.o.p ( m.pri ) ;

package p1 ;class Myclass

private int pri = 10 ;public int pub = 20 ;protected int pro = 30 ;int no = 40 ;Myclass( )

S.o.p ( m.pub ) ;S.o.p ( m.pro ) ;S.o.p ( m.no ) ;

DefaultError

Works

For same package's subclass the behaviour is same

Different Package's Classpackage p2 ;import p1.Myclass ;public class Second


Myclass m = new Myclass( ) ;S.o.p ( m.pri ) ;S.o.p ( m.pub ) ;S.o.p ( m.pro ) ;S.o.p ( m.no ) ;

package p1 ;public class Myclass

private int pri = 10 ;public int pub = 20 ;protected int pro = 30 ;int no = 40 ;public Myclass( )

WorksError

Different Package's SubClasspackage p1 ;public class Myclass

private int pri = 10 ;public int pub = 20 ;protected int pro = 30 ;int no = 40 ;public Myclass( )

package p2 ;import p1.Myclass ;public class Second

extends Myclass


Second m = new Second( ) ;S.o.p ( m.pri ) ;S.o.p ( m.pub ) ;S.o.p ( m.pro ) ;S.o.p ( m.no ) ;

ErrorWorks


Summary

Same Class

Same Package Class

Different package Class

Different package Subclass

Same Package Subclass

Private No modifier Protected PublicAccessible to


Effective IO - IYashavant Kanetkar

[email protected]

Objectives♦ Expectations from an IO system♦ How does Java meet these expectations♦ What is stream-based IO model♦ Different types of streams♦ Program to illustrate the difference

Expectations From An IO SystemI should be able to comm. with diff. sources & destination

I should be capable to I/O varied entities

FileKeyboardConsole

Network Port

Printer

Java Program

BytesCharacters

Lines Numbers

RecordsObjects

Java Program


Expectations From An IO SystemI should be able to communicate in multiple ways

I should be capable of dealing with underlying file system

Sequential AccessRandom Access

Java Program

Permissions

Paths

Times Dates

Files Directories

Java Program

♦ A program can read from a stream or write to a stream♦ Streams hide the details of communication from you♦ Streams are linked to physical devices by Java IO system♦ Streams are implemented using classes in java.io package

Java Solution♦ Perform all IO using Streams♦ Stream is a sequence of bytes that travel from

source to destination over a communication path

Source Java Program

Input Stream

001011

DestinationJava Program

Output Stream

110011

Impl. changes as per deviceMethods used are same

♦ Two types of streams – Byte and Character♦ Byte streams perform i/o one byte at a time♦ Character streams perform i/o one char (2 bytes) at a time♦ Byte streams are used to i/o binary data♦ Character stream are used to i/o text data♦ java.io package has many classes for these streams♦ File utility classes are also present

Byte & Character Streams

Expectations 1,2,3

Expectation 4


Object

Byte Streams (Binary IO)

FileOutputStream

FilterOutputStream

...

FileInputStream

FilterInputStream

...DataInputStream

BufferedInputStream

DataOutputStream

BufferedOutputStream

PrintStream

♦ InputStream, OutputStream - Abstract classes♦ FileInputStream, FileOutputStream - R/W streams of bytes from file♦ FilterInputStream - Uses some input stream as source of data

It filters data for contained stream♦ BufferedInputStream - Provides buffering ability♦ DataInputStream - Provides ability to read Java primitives

InputStream

OutputStream

Character Streams (Text IO)

Object

FileReader

FileWriter

Reader

Writer

BufferedReader

InputStreamReader

...

BufferedWriter

OutputStreamWriter

PrintWriter

...

♦ Reader, Writer - Abstract classes♦ InputStreamReader, OutputStreamWriter - R/W char from/to stream♦ FileReader, FileWriter - R/W characters from/to file♦ PrintWriter - Formatted writing in text representation

package basicio ;import java.io.* ;public class BasicIO

public static void main ( String[ ] args ) throws IOException

int i = 123456 ;RawWrite ( i ) ; CharWrite ( i ) ; UnicodeWrite ( i ) ;

static void RawWrite ( int i ) throws IOException

DataOutputStream ds = new DataOutputStream ( new FileOutputStream ( "Stream.txt" ) ) ;

ds.writeInt ( i ) ; ds.close( ) ; S.o.p ( new File ( "Stream.txt" ).length( ) ) ;

Difference - Byte & Char Streams

Contd...

FileOutputStream

DataOutputStream

4614


static void CharWrite ( int i ) throws IOException

FileWriter fw = new FileWriter ( new File ( "Char.txt" ) ) ; fw.write ( ( ( Integer ) i ).toString( ) ) ; fw.close( ) ; S.o.p ( new File ( "Char.txt" ).length( ) ) ;

static void UnicodeWrite ( int i ) throws IOException

OutputStreamWriter ow = new OutputStreamWriter ( new FileOutputStream ( "CharU.txt" ), "UTF-16" ) ;

ow.write ( ( ( Integer ) i ).toString( ) ) ; ow.close( ) ; S.o.p ( new File ( "CharU.txt" ).length( ) ) ;

... Contd.

File

FileWriter

FileOutputStreamOutputStreamWriter

Necessary


Effective IO - IIYashavant Kanetkar

[email protected]

Objectives

♦ Meaning of common IO code snippets♦ Working of Stream IO♦ Reading Strings♦ Record IO

What Were We Using...

import java.io.* ;

System.out.println ( "Hello" ) ;System.out.print ( "Hi" ) ;

int ch ;ch = System.in.read( ) ;

Package

Class PrintStream obj. reference

InputStream obj. reference

public static data members

Derived from OutputStream


InputStreamReader ir ;ir = new InputStreamReader ( System.in ) ;BufferedReader b ;b = new BufferedReader ( ir ) ;String s ;s = b.readLine( ) ;

What Happens When...

BufferedReader

InputStreamReader

System.inConverts bytes to charsFilters out CR & LF

Reads bytes - stream

Buffers filtered characters

public class Charread

static public void main ( String args[ ] )

class ISR

InputStream q ;ISR ( InputStream p )

q = p ;

class BR

ISR j ;BR ( ISR i )

j = i ;

class InputStream

readLine( )

ISR ir ;ir = new ISR ( System.in ) ;BR b ;b = new BR ( ir ) ;

fun1( )

q.readLine ( str ) ;

s = b.readLine( ) ;

readLine( )

j.fun1( ) ;

// filter CR & LF and returns str

// put chars into buffer & ret.

// reads byte // from stream// and returns it

BufferedReader

InputStreamReader

System.in

public class ReadTest


File f = new File ( "src/readtest/ReadTest.java" ) ;if ( f.exists( ) && f.canRead( ) )

BufferedReader br = null ;try

br = new BufferedReader ( new FileReader ( f ) ) ;String line ;while ( ( line = br.readLine( ) ) != null )

System.out.println ( line ) ;

Reading Strings From File

Contd...

Don't put this in try block

Might throw FileNotFoundException

Might throw IOException


catch ( FileNotFoundException ex )

S.o.p ( "Can't open " + f.getName( ) + " for rdg." ) ; finally

if ( br != null )br.close( ) ;

…Contd.

import java.io.* ;public class Empinfo

static public void main ( String args[ ] ) throws IOException

FileOutputStream fos ;fos = new FileOutputStream ( "emp.dat" ) ;BufferedOutputStream bos ;bos = new BufferedOutputStream ( fos ) ;DataOutputStream dos ;dos = new DataOutputStream ( bos ) ;

Record IO

InputStreamReader isr1 ;isr1 = new InputStreamReader ( System.in ) ;BufferedReader br1 = new BufferedReader ( isr1 ) ;

FormattedBuffered o/p

Contd...

DataOutputStream

BufferedOutputStream

FileOutputStreamBuffers data

Writes to a file

Writes Std. data

For Console input

String choice = "y", temp ;while ( choice.equals ( "y" ) )

S.o.p ( "Enter employee id: " ) ;temp = br1.readLine( ) ;dos.writeInt ( Integer.parseInt ( temp ) ) ;

S.o.p ( "Enter employee salary: " ) ;temp = br1.readLine( ) ;dos.writeDouble ( Double.parseDouble ( temp ) ) ;

S.o.p ( "Enter employee name: " ) ;temp = br1.readLine( ) ;dos.writeBytes ( temp + "\n" ) ;

S.o.p ( "Want another ( y/n ): " ) ;choice = br1.readLine( ) ;

dos.close( ) ;

…Contd.

Contd...


FileInputStream fis ;fis = new FileInputStream ( "emp.dat" ) ;BufferedInputStream bis ;bis = new BufferedInputStream( fis ) ;DataInputStream dis ;dis = new DataInputStream( bis ) ;

FormattedBuffered

input

For readingString

InputStreamReader isr2 ;isr2 = new InputStreamReader ( dis ) ;BufferedReader br2 ;br2 = new BufferedReader ( isr2 ) ;

…Contd.

Contd...

String s ;int i = 1 ;S.o.p ( "\nEmployees Info: " ) ;while ( true )

S.o.p ( dis.readInt( ) ) ;S.o.p ( dis.readDouble( ) ) ;dis.mark ( 0 ) ;s = br2.readLine( ) ;S.o.p ( s ) ;dis.reset( ) ;dis.skipBytes ( s.length( ) + 1 ) ;br2.skip ( 12 ) ;i++ ;

…Contd.



Effective IO - IIIYashavant Kanetkar

[email protected]


Objectives

♦ How to recursively list files♦ How to access Filesystem attributes♦ How to create our own filters


package dirread ;import java.io.* ;public class DirRead

static final long OneKb = 1000L ;static final long OneMeg = 1000000L ;static final long OneGig = 1000000000L ;public static void main ( String[ ] args )

listFiles ( new File ( "." ), "" ) ;

Listing Files build/classes/fileio/BasicIO.class [ 1K ]DirRead.class [ 2K ]FileIOTest.class [ 1K ]ReadTest.class [ 1K ]SysPropTest.class [ 588 ]WriterTest.class [ 3K ]

depcache/dependencies.txt [ 1K ]

dist/FileIO.jar [ 12K ]README.TXT [ 1K ]

Recursive Function

Contd...

Directories

Size



public static void listFiles ( File f, String indent )

System.out.println ( indent + f.getName( ) + "/" ) ;File[ ] list ;try

list = f.listFiles( ) ; catch ( SecurityException se )

return ;for ( File ch : list )

if ( !ch.isDirectory( ) ) System.out.println ( indent + " " +

ch.getName( ) + " [ " + getSize ( ch ) + " ]" ) ;

build/classes/fileio/BasicIO.class [ 1K ]DirRead.class [ 2K ]FileIOTest.class [ 1K ]ReadTest.class [ 1K ]SysPropTest.class [ 588 ]WriterTest.class [ 3K ]



Contd...


for ( File ch : list )

if ( ch.isDirectory( ) )listFiles ( ch, indent + " " ) ;

build/classes/fileio/BasicIO.class [ 1K ]DirRead.class [ 2K ]FileIOTest.class [ 1K ]ReadTest.class [ 1K ]SysPropTest.class [ 588 ]WriterTest.class [ 3K ]



Contd...

…Contd.


public static String getSize ( File f )

String szStr = "" ; long size = f.length( ) ;if ( size < OneKb )

return Long.toString ( size ) ;if ( size > OneGig )

szStr = szStr + Long.toString ( size / OneGig ) + "," ;size = size % OneGig ;

if ( size > OneMeg )

szStr = szStr + Long.toString ( size / OneMeg ) + "," ;size = size % OneMeg ;

if ( size > OneKb )

szStr = szStr + Long.toString ( size / OneKb ) + "K" ;return szStr ;



package fileiotest ;import java.io.* ;import java.security.* ;public class FileIOTest


String fName = "FileIOTest.txt" ;File f = new File ( fName ) ; try

f.createNewFile( ) ;f.setReadOnly( ) ;// Following statement should generate an exceptionFileWriter fw = new FileWriter ( f ) ;fw.close( ) ;

File Class Usage

Contd...


catch ( FileNotFoundException fne )

f.setWritable ( true, true ) ; // Make writable for owner onlyFileWriter fw = null ;try

fw = new FileWriter ( f ) ;fw.write ( "Hello World\n" ) ;S.o.p ( "Wrote to " + fName ) ;S.o.p ( f.getAbsolutePath( ) ) ;File d ;d = new File ( "d1" ) ;d.mkdir( ) ;// Recursively build entire pathd = new File ( "d2/d3/d4" ) ;d.mkdirs( ) ;

…Contd.

finally

fw.close( ) ;


Filter Streams

BufferedReader

UppercaseReader

FileReader

abcdefghijk

ABCDEFGHIJK

Upper-case Filter

Reader

FilterReader

Abstract



Uppercase Filterpackage uppercasereader ;import java.io.* ;public class UppercaseReader extends FilterReader

public static void main ( String[ ] args ) throwsFileNotFoundException, IOException

File f = new File ( "src/fileio/UppercaseReader.java" ) ;if ( f.exists( ) && f.isFile( ) && f.canRead( ) )

BufferedReader br = new BufferedReader ( newUppercaseReader ( new FileReader ( f ) ) ) ;

String line ;while ( ( line = br.readLine( ) ) != null )

System.out.println ( line ) ;

BufferedReader

UppercaseReader

FileReader


public UppercaseReader ( Reader in )

super ( in ) ;private int transform ( int ch )

if ( ch != -1 && Character.isLowerCase ( ch ) ) return Character.toUpperCase ( ch ) ;

return ch ;public int read( ) throws IOException

int ch = in.read( ) ;return transform ( ch ) ;

Helper Functions

Reads one char

Underlying characterinput stream

protected Reader in In FilterReader


public int read ( char[ ] cbuf, int off, int len ) throws IOException

int rc = in.read ( cbuf, off, len ) ;for ( int i = off ; i < off + rc ; i++ )

cbuf [ i ] = ( char ) transform ( cbuf [ i ] ) ;return rc ;

Helper FunctionsReads characters in

a portion of array- Start from where- Read how many

Returns how many charsare read succesfully


Filter & Other StreamsYashavant Kanetkar

[email protected]

Objectives

♦ Input and Output Filters♦ How to create output filters♦ What are predefined streams♦ Streams overview♦ Tokenizer program

Interface ITransform

int transform ( int ch ) ;

Encrypt / Decrypt Filter

abcdefghijk

fhkzmdcbnoy

Common Filter

Encrypt

Decrypt

Uses Substitution Cipher

Encrypt Decrypt


Encryptionpackage fileio ;import java.io.* ;interface ITransform

int transform ( int ch ) ;class Encrypt implements ITransform

static final String str = "xyfagchbimpourvnqsdewtkjzl" ;public int transform ( int ch )

if ( Character.isLowerCase ( ch ) )ch = str.charAt ( ch - 'a' ) ;

return ch ;

Returns charin the string

If ch = 'b'

ch – 'a'

1

y

Decryption

class Decrypt implements ITransform

static final String str = "xyfagchbimpourvnqsdewtkjzl" ;public int transform ( int ch )

if ( Character.isLowerCase ( ch ) ) ch = str.indexOf ( ch ) + 'a' ;

return ch ;

Must be sameas in Encrypt( )

Returns positionin the string

If ch = 'y'

1

1 + 'a'

b

TransformWriter Class

public class XformWriter extends FilterWriter

public static void main ( String[ ] args) throws IOExceptiondoEncDec ( "src/fileio/XformWriter.java", "enc.txt", true ) ;doEncDec ( "enc.txt", "dec.txt", false ) ;

// more functions here

XformWriter.java enc.txtEncrypt

dec.txtDecrypt


public static void doEncDec ( String s, String t, boolean flag ) throws IOException

XformWriter out = new XformWriter ( new PrintWriter ( t ),

flag ? new Encrypt( ) : new Decrypt( ) ) ;File f = new File ( s ) ;BufferedReader br = new BufferedReader ( new FileReader ( f ) );String line ;

String sep = System.getProperty ( "line.separator" ) ;while ( ( line = br.readLine( ) ) != null )

out.write ( line + sep ) ;out.close( ) ;

private ITransform trans = null ;public XformWriter ( PrinterWriter out, ITransform t )

super ( out ) ; this.trans = t ;

Driver Fun.

XformWriter

PrintWriter

BufferedReader

FileReader

write( )spublic void write ( int c ) throws IOException

out.write ( trans.transform ( c ) ) ;public void write ( char[ ] ch, int off, int len )

throws IOException

for ( int i = off ; i < off + len ; i++ )ch [ i ] = ( char ) trans.transform ( ch[ i ] ) ;

super.write ( ch, off, len ) ;public void write ( String str, int off, int len )

throws IOException

char[ ] ch = str.toCharArray( ) ;write ( ch, off, len ) ;

The Predefined streams

♦ java.lang package defines a class called System♦ It contains three predefined public static var. - in, out, err♦ They are accessible from any part of the program ♦ System.out refers to standard output stream (console)♦ System.in refers to standard input stream (keyboard)♦ System.err refers to standard error stream (console)♦ These streams are already open & ready to supply/accept

input/output data


Streams Overview

♦ Five group of classes are defined in java.io♦ For building different types of byte & character streams♦ For filtering and piping♦ For reading/writing primitive values and strings♦ For Interacting with files♦ For object serialization

♦ Reader provides a char.stream analogous to byte stream InputStream♦ Writer provides a char. stream analogous to byte stream OutputStream♦ Methods of Reader mirror those of InputStream♦ Methods of Writer mirror those of OutputStream♦ InputStreamReader & OutputStreamWriter are converter classes♦ They translate between character and byte streams ♦ They use either a specified character set encoding or the default

encoding for the local system

♦ Streams that have i/o pairs + byte stream & character stream variants♦ Filter streams♦ Buffered streams

♦ In-memory streams:♦ ByteArray streams♦ CharArray streams♦ String streams

♦ I/O Streams that have no O/I counterpart:♦ The Print streams♦ LineNumberReader♦ SequenceInputStream

♦ Streams that are useful for building parsers♦ Pushback streams♦ Tokenizer streams

Specials Streams

- Parse input stream into "tokens"- Allows tokens to be read one at a time

Represents concatenationof underlying input streams

- Lets you push back, or “unread” chars- Useful for breaking input into tokens

Simple Tokenizer

Gomadic charged us 27.50$ for Ipaq charger.(However they didn't provide the Tracking number.)

Tokens.txt

(1) Gomadic(1) charged(1) us(1) 27.5(1) $(1) for(1) Ipaq(1) charger(1) .(2) ((2) However(2) they(2) didn't(2) provide(2) the(2) Tracking(2) number(2) .(2) )


Program

package mytokenizer ;import java.io.* ;public class MyTokenizer

public static void main ( String args[ ] ) throws Exception

FileReader fr = new FileReader ( "tokens.txt" ) ;BufferedReader br = new BufferedReader ( fr ) ;StreamTokenizer st = new StreamTokenizer ( br ) ;

st.ordinaryChar ( '.' ) ;st.wordChars ( '\'', '\'' ) ;while ( st.nextToken( ) != StreamTokenizer.TT_EOF )

switch ( st.ttype )

Recognizes:IdentifiersNumbersStringsComments

Treat . as a ordinary character

Treat ' as part of word

case StreamTokenizer.TT_WORD :S.o.p ( "(" + st.lineno( ) + ") " + st.sval ) ;break ;

case StreamTokenizer.TT_NUMBER :S.o.p ( "(" + st.lineno( ) + ") " + st.nval ) ;break ;

default :S.o.p ( "(" + st.lineno( ) + ") " + ( char ) st.ttype ) ;

fr.close( ) ;


SerializationYashavant Kanetkar

[email protected]

Objectives

♦ What is Serialization & Deserialization♦ Where is it useful♦ How to Serialize selectively♦ Problems in selective Serialization♦ How to overcome the selective Serialization problems♦ Program to illustrate Serialization of a collection

Serialization

♦ Storing objects persistently♦ Store in a form that Restoration becomes possible♦ While reconstructing, Ctor is not called♦ Use 1 - Inter-process communication becomes simple♦ Use 2 - Storing objects in database♦ Use 3 - Profiles / Preferences - Example myYahoo

Time of obj. creationIdNamePrice

Cart.datSerialization

Deserialization


Programpackage serialization1 ;import java.io.* ;import java.util.* ;public class Serialization1

static final String fname = "cart.dat" ;public static void main ( String[ ] args ) throws IOException,

ClassNotFoundException, InterruptedException

Product p1, p2 ;p1 = new Product ( 1, "Quest", 500.0f ) ;saveObject ( p1 ) ;Thread.sleep ( 2000 ) ;p2 = restoreObject( ) ;System.out.println ( p1 ) ;System.out.println ( p2 ) ;

[ Wed Oct 24 14:25:24 IST 2007, 1, Quest, 500.0 ][ Wed Oct 24 14:25:24 IST 2007, 1, Quest, 500.0 ]

Do nothing for next 2 seconds

Save and Restore

static void saveObject ( Product p ) throws IOException

ObjectOutputStream out ;out = new ObjectOutputStream( new FileOutputStream(fname));out.writeObject ( p ) ;out.close( ) ;

static Product restoreObject( ) throws IOException,

ClassNotFoundException

ObjectInputStream in ;in = new ObjectInputStream ( new FileInputStream ( fname ) ) ;Product p = ( Product ) in.readObject( ) ;in.close( ) ;return p ;

Product Classclass Product implements Serializable

private int id ; private String Name ;private float price ; private Date creationTime ;public Product( )

creationTime = new Date( ) ; S.o.p ( " 0-arg Ctor" ) ;public Product ( int num, String name, float p )

creationTime = new Date( ) ;id = num ; Name = name ; price = p ; S.o.p ( "3-arg Ctor" ) ;

public String toString( )

return "[ " + creationTime + ", " + id + ", " +Name + ", " + price + " ]";


Transient Dataclass Product implements Serializable

private int id ; private String Name ; private float price ; transient private Date creationTime ;public Product( )

..public Product ( int num, String name, float p )

..public String toString( )

..

[ Wed Oct 24 14:35:15 IST 2007, 1, Quest, 500.0 ][ null, 1, Quest, 500.0 ]

Solutionclass Product implements Serializable

private int id ; private String Name ; private float price ;transient private Date creationTime ;

// 0-arg Ctor// 3-arg Ctor// toString( ) method

private void readObject ( ObjectInputStream in )throws IOException, ClassNotFoundException

in.defaultReadObject( ) ;creationTime = new Date( ) ;

[ Wed Oct 24 14:34:28 IST 2007, 1, Quest, 500.0 ]

[ Wed Oct 24 14:34:30 IST 2007, 1, Quest, 500.0 ]

Product List Serializationpackage serialization2 ;import java.io.* ;import java.util.* ;public class Serialization2

static final String fname = "cart.dat" ;public static void main ( String[ ] args )

throws IOException, ClassNotFoundException, InterruptedException

ProductList pl1 = new ProductList( ) ;saveObjectList ( pl1 ) ;Thread.sleep ( 2000 ) ;ProductList pl2 ;pl2 = restoreObjectList( ) ;System.out.println ( pl1 ) ;System.out.println ( pl2 ) ;

[[ [ Wed Oct 24 14:41:25 IST 2007, 0, Quest0, 550.0 ][ Wed Oct 24 14:41:25IST 2007, 1, Quest1, 550.0 ] ]][[ [ Wed Oct 24 14:41:27 IST 2007, 0, Quest0, 550.0 ][ Wed Oct 24 14:41:27IST 2007, 1, Quest1, 550.0 ] ]]


Save & Restorestatic void saveObjectList ( ProductList p ) throws IOException

ObjectOutputStream out ;out = new ObjectOutputStream ( new FileOutputStream (

fname ) ) ;out.writeObject ( p ) ;out.close( ) ;

static ProductList restoreObjectList( ) throws IOException,

ClassNotFoundException

ObjectInputStream in ;in = new ObjectInputStream ( new FileInputStream( fname ));ProductList p = ( ProductList ) in.readObject( ) ;in.close( ) ;return p ;

...Contd.

Product Classclass Product implements Serializable

private int id ; private String Name ; private float price ;transient private Date creationTime ;public Product( )

creationTime = new Date( ) ;public Product ( int num, String name, float p )

creationTime = new Date( ) ;id = num ; Name = name ; price = p ;


return "[ " + creationTime + ", " + id + ", " +Name + ", " + price + " ]";

Contd...

Product Class Contd.

private void readObject ( ObjectInputStream in )throws IOException, ClassNotFoundException

in.defaultReadObject( ) ;creationTime = new Date( ) ;

...Contd.


ProductList Classclass ProductList implements Serializable

Product[ ] plist = new Product [ 2 ] ;public ProductList( )

for ( int i = 0 ; i < plist.length ; i++ )plist[ i ] = new Product ( i, "Quest" + i, 550.0f ) ;


StringBuilder sb = new StringBuilder( ) ;sb.append ( "[[ " ) ;for ( int i = 0 ; i < plist.length ; i++ )

sb.append ( plist [ i ] ) ;sb.append ( " ]]" ) ;return sb.toString( ) ;


Collection ClassesYashavant Kanetkar

[email protected]

Objectives

Ω Why do we need Collections

Ω Cornerstones of Collections

Ω Advantages of using Collections

Ω Types of Collections

Ω Using the Vector collection

Store n Integers

55 63 28 45 60 N

No point in implementing Array and Linked List ourselves

Array of n itemsn Variables Linked List

Too tedious Wastage, Resizing Difficult

Data Link


Philosophy

Access

Storage

Operations

LinearNon-linear

setgetaddremoveinsert

subsetsort, searchreversecopyfrequencymin, maxfill, zero...

Solution - Collections

Reduced effort – Don't reinvent the wheelPerformance – Efficient AlgorithmsSimilarity – Similar operations on diff. types / collectionsExtensibility – Easy adaptation for new objectsReuse – Different libraries use same collection classes

WhereWhat Why

ObjectGroup > 1 element

Store, RetrieveModify, Transmit Performance

Similarity

Reduced effort

ReuseExtensibility

Collection Types

IndexedOrdered Mapped

IO is order based

Stack, Queue

IO is index based

ArrayList, Vector

IO is key based

HashT, Tree Map


How To Represent & Manage Collections

Interfaces

Declarations

Implementations

Collection classes

Algorithms

Static Methods

Interfaces

Collection

Iterable Iterator Map

ListIterator SortedMap

DequeueSortedSet

ListSet Queue

Iterable – iterator( ) - Returns the Iterator objectIterator – hasNext( ), next( ), remove( )Map – <key, value> pairs. Ex. Dictionary, Address bookListIterator – hasPrevious( ), previous( ), ..

Collection Classes

AbstractCollection PriorityQueueAbstractQueue

AbstractList

AbstractSet

Stack

LinkedList

HashSet

TreeSet

Abs.Seq.List

ArrayList

Vector


Algorithms

CollectionsArrays

binarySearch( )

copyRange( )

sort( )

fill( )

...

max( )

reverse( )

min( )

copy( )

shuffle( )

...

package collections ;import java.io.* ;import java.util.* ;public class VectorTest


Vector v1 = new Vector( ) ;v1.add ( 'b' ) ; v1.add ( 4 ) ;Vector v2 = new Vector( ) ;v2.add ( "Hello" ) ; v2.add ( "World" ) ;v1.addAll ( v2 ) ; v1.add ( 8.7 ) ;v1.add ( "Rahul" ) ; v1.add ( 1 , "Deepti" ) ;

S.o.p ( v1.size( ) ) ;S.o.p ( v1.capacity( ) ) ;if ( v1.contains ( "Deepti" ) )

S.o.p ( "Found Deepti" ) ;v1.remove ( "Rahul" ) ;Iterator e = v1.iterator( ) ;while ( e.hasNext( ) )

S.o.p ( e.next( ) ) ;

Vector

Count: 7Capacity: 10

Add items from v2

bDeepti4HelloWorld8.7

Variable len. arrayResizableOrdered CollectionThread-safe


Collections & Inner ClassesYashavant Kanetkar

[email protected]

Objectives

Ω How to use ArrayList CollectionΩ Collection of user-defined typesΩ Relationship between Inner Classes and CollectionsΩ How to use key-value collections

ArrayList Collectionpackage collections ;import java.util.* ;import java.io.* ;public class ArrayListTest


ArrayList arr = new ArrayList( ) ;arr.add ( 'a' ) ;arr.add ( 43 ) ;arr.add ( 6.7 ) ;arr.add ( "Rahul" ) ;arr.add ( true ) ;arr.add ( 1, "Deepti" ) ;S.o.p ( "Count: " + arr.size( ) ) ;arr.remove ( "Rahul" ) ;

Count: 6

Variable length arrayResizableOrdered CollectionNot thread-safeCan be synchronized

Boxed

Contd...


S.o.p ( "Index of 6.7 : " + arr.indexOf ( 6.7 ) ) ;S.o.p ( "Element at Index 0 : " + arr.get ( 0 ) ) ;

Iterator e = arr.iterator( ) ;while ( e.hasNext( ) )

S.o.p ( e.next( ) ) ;

Collections.reverse ( arr ) ;e = arr.iterator( ) ;while ( e.hasNext ( ) )

S.o.p ( e.next( ) ) ;

aDeepti436.7True

True6.743Deeptia

IteratorInterfacePermits AccessCan modify

..Contd. Index of 6.7 : 3Element at Index 0 : a

ConcurrentModificationException

TreeSetpackage collections ;import java.util.* ;import java.io.* ;public class TreeSetTest


TreeSet ts = new TreeSet( ) ;ts.add ( new Product ( 3, "J2EE" ) ) ;ts.add ( new Product ( 2, "Data Structures" ) ) ;ts.add ( new Product ( 4, "C#" ) ) ;ts.add ( new Product ( 1, "Embedded" ) ) ;Iterator e = ts.iterator( ) ;while ( e.hasNext( ) )

System.out.println ( e.next( ) ) ;

Contd...

Ordered CollectionSorted by nat. orderNo duplication

class Product implements Comparable

private int id ;private String name ;

public Product ( int i , String n )

this.id = i ; this.name = n ;


return "< " + this.id + ", " + this.name + " >" ;

..Contd.

Contd...


public int compareTo ( Object o )

assert o instanceof Product ;Product p2 = ( Product ) o ;return name.compareTo ( p2.name ) ;

public boolean equals ( Object o )

assert o instanceof Product ;Product p2 = ( Product ) o ;return name == p2.name && id == p2.id ;

..Contd. assert – keywordinstanceof – keyword

For Interface

For Base Class

Inner Classesclass Outer

int x = 100 ;class Inner

int y = 50 ;void display( )

S.o.p ( y + " " + x ) ;

public class Sample

public staticvoid main ( String args[ ] )

Inner i = new Inner( ) ;i.display( ) ;S.o.p ( i.y ) ;Outer o = new Outer( ) ;o.fun( ) ;

void fun( )

Inner i = new Inner( ) ;i.display( ) ;S.o.p ( i.y ) ;

Inner class objects must be createdthrough Outer class functionInner class can access Outer class fields & methods

One More Access

class Outer

public class Sample

public staticvoid main ( String args[ ] )

Outer o = new Outer( ) ;

Inner fun( )

Inner i = new Inner( ) ;return i ;

interface test

void display( ) ;

class Inner impements test


S.o.p ( "Hi" ) ;

t.display( ) ;test t = o.fun( ) ;

Works

Inner class can be accessed form outside the Outer class

using an interface pointer


class TreeSetItr implements Iterator

// end of TreeSetItr class

boolean hasNext( )

// logic to check if next node exists in the tree set or not

class TreeSet Implements Iterable

How It WorksIterator iterator( )

// creates object of TreeSetItr// returns its reference

// end of TreeSet class

Object next( )

// go to next node in the tree set// returns next Product object in the tree set as an Object

Iterator e = ts.iterator( ) ;while ( e.hasNext( ) )

S.o.p ( e.next( ) ) ;


Generics / TemplatesYashavant Kanetkar

[email protected]

Objectives

Ω Need for generalized Collections

Ω What are Generics

Ω How to use Generic Collections

Ω How to create user-defined generic collection

Requirement

Task:Manage a collection of Products

Store Product objects in a

ArrayList

Store Product

objects in a LinkedList


Product Class

class Product

private int id ;private String name ;

public Product ( int i, String n )

name = n ;id = i ;


S.o.p ( id + " " + name ) ;

Dump Into ArrayListpackage templates ;import java.util.* ;public class Templates1


ArrayList ts = new ArrayList( ) ;ts.add ( new Product ( 1, "P1" ) ) ;ts.add ( "hello" ) ;ts.add ( new Product ( 2, "P2" ) ) ;Iterator i = ts.iterator( ) ;while ( i.hasNext( ) )

Product p = ( Product ) i.next( ) ;p.display( ) ;

1 P1ClassCastException: String can't be cast to Product

Heterogeneous - Bad ideaUnless in a inheritance chain

Buggy - Compilation OKSlow - Only objectsUgly -Typecasting

Solutions

Ω Sol. 1 - Create different ArrayList classes for different types

Ω Sol. 2 - Create one Generic ArrayList class for all types

Ω Generics were invented for implementing generic collections

Ω Many other J2SE libraries use them

Ω Generics refers to Generic types & Generic methods

Ω Generics types & methods differ from regular types and methods in that they have type parameters

Code Specialisation Code Sharing


package templates ;import java.util.* ;public class Templates2


ArrayList <Product> pl = new ArrayList <Product> ( ) ;pl.add ( new Product ( 1, "P1" ) ) ;// pl.add ( "hello" ) ;pl.add ( new Product ( 2, "P2" ) ) ;Iterator <Product> i = pl.iterator( ) ;while ( i.hasNext( ) )

Product p = i.next( ) ;p.display( ) ;

Generic ArrayList

- Compilation error- Ensures homogenity- Typesafe collections

- Generic ArrayList. Other Coll. too- Generic types have type parameters- Formal types replaced by actual types

- Compiles without errors- No ClassCastExceptions at runtime

Generics - TipsΩ 3 ways to use generic collection types

Ω Concrete instantiation - with concrete type argumentsArrayList <Product> pl = new ArrayList <Product> ( ) ;

Ω Raw instantiation - without type argumentsArrayList pl = new ArrayList( ) ;

Ω Wildcard instantiation - with wildcard argumentsBeyond scope

Ω Advantages of GenericsΩ Increased expressive powerΩ Improved type safetyΩ Implicit type checks and type conversions where needed

Ω Downside: Ω No primitive types

MyCollection td = new MyCollection( ) ;

td.add ( 5.7f ) ;td.add ( "Hello" ) ;S.o.p ( td.get ( 1 ) ) ;S.o.p ( td.get ( 0 ) ) ;

User-Def. Genericpackage templates ;import java.util.* ;public class Templates3


MyCollection <Integer> ti = new MyCollection <Integer>( ) ;

ti.add ( 5 ) ;ti.add ( 10 ) ;S.o.p ( ti.get ( 1 ) ) ;S.o.p ( ti.get ( 0 ) ) ;

MyCollection<Product> tp = new MyCollection<Product>( ) ;

tp.add ( new Product ( 1 , "P1" ) ) ;tp.add ( new Product ( 1 , "P2" ) ) ;tp.get ( 1 ).display( ) ;tp.get ( 0 ).display( ) ;

10 5

Type casting not reqd.1 P21 P1

Hello5.7

- Unsafe instantiation- Works without 'type' parameter- Allows 'heterogenous' collections- Bad idea though!


MyCollectionclass MyCollection<E>

private ArrayList<E> items ;

public MyCollection( )

items = new ArrayList<E>( ) ;public void add ( E obj )

items.add ( obj ) ;public E get ( int i )

return items.get ( i ) ;

- E is Placeholder for any type- E is similar to a type- But not really a type- Restrictions:• Cannot be used in new• Can't be derived from

Product class:- 2-arg Ctor- display( )


User-defined GenericsYashavant Kanetkar

[email protected]

Objectives

Ω How to create user-defined Collections

Ω How to create user-defined Iterators

Ω How to create a generic printList( ) algorithm

Ω How to create a Function Template

User-Defined Iteratorpackage templates ;import java.util.* ;public class Templates4


TCollection<Product> pl = new TCollection<Product> ( ) ;pl.add ( new Product ( 1, "P1" ) ) ;pl.add ( new Product ( 2, "P2" ) ) ;pl.add ( new Product ( 3, "P3" ) ) ;pl.add ( new Product ( 4, "P4" ) ) ;pl.add ( new Product ( 5, "P5" ) ) ;pl.add ( new Product ( 5, "P6" ) ) ;for ( Product p : pl )

p.display( ) ;

1 P12 P23 P34 P45 P55 P6

Product class:- 2-arg Ctor- display( )

Iterator<Product> i = pl.iterator( ) ;

while ( i.hasNext( ) )

Product p = i.next( ) ;p.display( ) ;


class TCollection<E> implements Iterable<E>

private ArrayList<E> items ;public TCollection( )

items = new ArrayList<E>( ) ;public void add ( E obj )

items.add ( obj ) ;public E get ( int i )

return items.get ( i ) ;public Iterator<E> iterator( )

return new TIterator ( this ) ;

Iterable Collec

Inner Classclass TIterator implements Iterator<E>

Iterator<E> itr ;public TIterator ( TCollection<E> c )

itr = c.items.iterator( ) ;public boolean hasNext( )

return itr.hasNext( ) ;public E next( )

return itr.next( ) ;public void remove( )

itr.remove( ) ;

Generic printList( ) Algorithmpackage templates ;import java.util.* ;public class Templates5


Vector<Integer> v = new Vector<Integer>( ) ;v.add ( 1 ) ; v.add ( 4 ) ;

ArrayList<Integer> al = new ArrayList<Integer>( ) ;al.add ( 2 ) ; al.add ( 6 ) ;

printIntList ( v ) ;printIntList ( al ) ;printList ( v ) ;printList ( al ) ;

1 42 6 1 4 2 6

Goal:Common printList( ) for all List<T> compatible classes

Can TCollection<T> use printList( ) ?Yes, if it implements java.util.List<T> interface


public static void printIntList ( List<Integer> tl )

for ( int a : tl )System.out.print ( a + " " ) ;

S.o.p( ) ;

public static<T> void printList ( List<T> tl )

for ( T a : tl )System.out.print ( a + " " ) ;

S.o.p( ) ;

Generic

More Generic

package templates ;import java.util.* ;public class Templates6

public static void main ( String [ ] args )

int a = 4 ; int b = 5 ;S.o.p ( "max = " + max ( a, b ) ) ;S.o.p ( "max = " + max ( 'z', 'y' ) ) ;S.o.p ( "max = " +

max ( new Product ( 1, "de" ), new Product ( 2, "bc" ) ) ) ;ArrayList<Integer> il = new ArrayList<Integer> ( ) ;il.add ( 10 ) ; il.add ( 20 ) ; il.add ( 30 ) ; il.add ( 20 ) ;S.o.p ( duplicate ( il ) ) ;ArrayList<Product> pl1 = new ArrayList<Product> ( ) ;pl1.add ( new Product ( 1, "P1" ) ) ;pl1.add ( new Product ( 2, "P2" ) ) ;pl1.add ( new Product ( 1, "P1" ) ) ;S.o.p ( duplicate ( pl1 ) ) ;

Function Templates

max = 5max = zmax = <1 , de >

public static <T extends Comparable> T max ( T a, T b ) if ( a.compareTo ( b ) < 0 )

return b ;return a ;

public static <T> boolean duplicate ( List<T> coll )

int count ;for ( T i1 : coll )

count = 0 ;for ( T i2 : coll )

if ( i1.equals ( i2 ) )count ++ ;

if ( count > 1 )

return true ;return false ;

Such a T thatimplements Comparable

Object contains equals( )It compares referencesWe want to compare valuesHence override equals( ) in T


Product Class Revisitedclass Product implements Comparable

private int id ;private String name ;public Product ( int id, String name )

name = name ;id = id ;


S.o.p ( id + " " + name ) ;public int compareTo ( Object o )

return name.compareTo ( ( ( Product ) o ).name ) ;

Program Continuedpublic boolean equals ( Object obj )

Product p2 = ( Product ) obj ;return name.equals ( p2.name ) ;

public int hashCode( )

int hash = 5 ;hash = 11 * hash + id ;hash = 11 * hash + ( name != null ? name.hashCode( ) : 0 ) ;return hash ;

Necessary once we override equals( )Computes HashcodeSufficiently sparse Empty in NetBeans 5.5Provided by NetBeans 6.0Asks which fields to use to compute hashcode


Networking Today Yashavant Kanetkar

[email protected]

Objectives

What an App needs to achieve network communicationNetwork programming modelHow to get HTTP headersHow to download a file using HTTPHow to download a file using FTP

Network Communication

Port NumberMachine Name Protocol

Gets converted to IP Address

To distinguish bet.communicating Apps

How to send requestHow to receive response

- 198.168.100.2- General to specific- 32-bit addresses- Network, Host- Class A, B, C

- Std. apps use std. port nos.- Different apps, different port nos.- 20, 21 – FTP 25 – SMTP- 110 – POP 80 – HTTP- No relation with serial, parallel ports


Network Programming Model

What we get to do?

Email C. Outlook, Eudora C. Email S. MS Exchange

POP/SMTP

Web C. IE, Firefox Web S. IIS, Apache

HTTP

FTP C. CuteFTP FTP S. Configured IIS

FTP

Client Server

How HTTP Works

Session

HTTP Response

Return Host IPReturn Host IP

Browser / App. Server

ISP DNS

Connection Req. Search DNS

HTTP Request

GET - Get a file from URLPOST - For sending dataOther - OPTIONS, HEAD, PUT, DELETE

Web Page – HTML + JavaScriptActiveX controlJava AppletAny requested file

Sample Header

Address : http://quest.ksetindia.com/null : [HTTP/1.1 200 OK]Date : [Sun, 28 Oct 2007 04:14:54 GMT]Transfer-Encoding : [chunked]Expires : [Thu, 19 Nov 1981 08:52:00 GMT]Set-Cookie : [osCsid=f5r28r4nvhl7qlecai71esmq93; path=/; domain=quest.ksetindia.com]Connection : [close]Content-Type : [text/html; charset=UTF-8]Server : [Apache/2.2.3 (Fedora)]X-Powered-By : [PHP/5.1.6]Cache-Control : [no-store, no-cache, must-revalidate, post-check=0, pre-check=0]

Response broken into chunks

200 OK - Request succeeded301 Moved Permanently 302 Moved Temporarily 404 Not Found500 Server Error

Server will close the connection following this response

Controls how proxies may cache this object

Key : Values(s) Pairs


HTTP Headerspackage networking ;import java.io.* ;import java.net.* ;import java.text.MessageFormat ;import java.util.* ;public class PrintHeaders


printHeaders ( "http://quest.ksetindia.com/index.php" ) ;printHeaders ( "http://microsoft.com/windows" ) ;printHeaders ( "http://quest.ksetindia.com/dl/myfile.zip" ) ;

Resource – File, Directory, Query URLs - HTTP, FTP, File, HTTPs..Uniform Resource Locator – Protocol://Location:portnumber/path/file

static void printHeaders ( String addr ) throws Exception

S.o.p ( MessageFormat.format ( "Address : 0", addr ) ) ;URL u = new URL ( addr ) ;HttpURLConnection conn ;conn = ( HttpURLConnection ) u.openConnection( ) ;if ( conn.getResponseCode( ) == HttpURLConnection.HTTP_OK)

Map<String, List<String>>headers = conn.getHeaderFields( );for ( String h : headers.keySet( ) )

S.o.p ( h + " : " + headers.get ( h ) ) ;conn.disconnect( ) ;

HTTPURLConnection - Derived from URLConnectionRepresents a comm. link between the app & HTTP URLUsing conn we can R/W to the resource referenced by URL

HTTP/1.0 200 OK HTTP/1.0 401 Unauthorized

Opens connectionMakes GET request

File Download

Client

HTTP Server

quest.ksetindia.com/dl/myfile.zip

FTP Server

quest.ksetindia.com/pub/myftp.zip

HTTP Request

FTP Request

Our App. Server


HTTP & FTP Downloadpackage networking ;import java.util.* ;import java.io.* ;import java.net.* ;public class HttpDownload

static final int BUF_SIZE = 100 ;public static void main ( String[ ] args ) throws Exception

URL u ;u = new URL ( "http://quest.ksetindia.com/dl/myfile.zip" ) ;HttpURLConnection conn ;conn = ( HttpURLConnection ) u.openConnection( ) ;if ( conn.getResponseCode( )==HttpURLConnection.HTTP_OK)

downloadFile ( conn.getInputStream( ), "myfile.zip" ) ;u = new URL ( "ftp://quest.ksetindia.com/pub/myftp.zip" ) ;downloadFile ( u.openStream( ), "myftp.zip" ) ;

Opens connection, Returns InputStream for rdg.

local filename

donwloadFile( ) static void downloadFile ( InputStream ins, String name )

throws Exception

S.o.p ( "Downloading: " + name ) ; BufferedInputStream fis = new BufferedInputStream ( ins ) ;FileOutputStream fos = new FileOutputStream ( name ) ;byte[ ] data = new byte[ BUF_SIZE ] ;int len ;while ( ( len = fis.read ( data, 0, data.length ) ) != -1 )

fos.write ( data, 0, len ) ;

fis.close( ) ;fos.close( ) ;S.o.p ( "Download completed: " + name ) ;


Networking & SecurityYashavant Kanetkar

[email protected]

Objectives

HTTP and FTP DownloadWhat is MD5Where is it usedWhat are its benefitsHow to use is programmatically

File Download

Client

HTTP Server

quest.ksetindia.com/dl/myfile.zip

FTP Server

quest.ksetindia.com/pub/myftp.zip

HTTP Request

FTP Request

Our App. Server


HTTP & FTP Downloadpackage networking ;import java.util.* ;import java.io.* ;import java.net.* ;public class HttpDownload


URL u ;u = new URL ( "http://quest.ksetindia.com/dl/myfile.zip" ) ;HttpURLConnection conn ;conn = ( HttpURLConnection ) u.openConnection( ) ;if ( conn.getResponseCode( )==HttpURLConnection.HTTP_OK)

downloadFile ( conn.getInputStream( ), "myfile.zip" ) ;u = new URL ( "ftp://quest.ksetindia.com/pub/myftp.zip" ) ;downloadFile ( u.openStream( ), "myftp.zip" ) ;

Opens connection, Returns InputStream for rdg.

local filename

donwloadFile( ) static void downloadFile ( InputStream ins, String name )

throws Exception

S.o.p ( "Downloading: " + name ) ; BufferedInputStream fis = new BufferedInputStream ( ins ) ;FileOutputStream fos = new FileOutputStream ( name ) ;byte[ ] data = new byte[ BUF_SIZE ] ;int len ;while ( ( len = fis.read ( data, 0, data.length ) ) != -1 )

fos.write ( data, 0, len ) ;

fis.close( ) ;fos.close( ) ;S.o.p ( "Download completed: " + name ) ;

MD5 ChecksumStands for Message-Digest algorithm 5Designed by Ronald Rivest in 1991Converts variable length content to a 128-bit valueOne way hash functionUsed in a wide variety of security applications:

Check integrity of filesStore passwords

MD5 hash is expressed as a 32-character hex numberA small change in the content gives a different 32-char hex no.


MD5 Checksum Logicmain( )

httpVerifyMD5( ) ftpVerifyMD5( )

downloadAnyFile( )

verifyChecksum( )

getChecksum( )

downloadHTTPFile( )

downloadAnyFile( )

Program

package networking ;import java.util.* ;import java.io.* ;import java.net.* ;import java.security.* ;public class VerifyMD5


httpVerifyMD5( ) ;ftpVerifyMD5( ) ;

static void ftpVerifyMD5( ) throws Exception

URL u = new URL ( "ftp://quest.ksetindia.com/pub/myftp.zip" ) ;downloadAnyFile ( u.openStream( ), u.toString( ) ) ;u = new URL ( "ftp://quest.ksetindia.com/pub/md5sum.txt" ) ;downloadAnyFile ( u.openStream( ), u.toString( ) ) ;verifyChecksum ( "myftp.zip" ) ;

HTTP Download And Verifystatic void httpVerifyMD5( ) throws Exception

downloadHTTPFile ( "http://quest.ksetindia.com/dl/myfile.zip" ) ;downloadHTTPFile ( "http://quest.ksetindia.com/dl/md5sum.txt" );verifyChecksum ( "myfile.zip" ) ;


downloadHTTPFile( )static void downloadHTTPFile ( String addr ) throws Exception

URL u = new URL ( addr ) ;HttpURLConnection conn ;conn = ( HttpURLConnection ) u.openConnection( ) ;if ( conn.getResponseCode( ) == HttpURLConnection.HTTP_OK )

downloadAnyFile ( conn.getInputStream( ), u.getFile( ) ) ;

downloadAnyFile( )static void downloadAnyFile ( InputStream ins, String name )

throws Exception

S.o.p ( "Downloading " + name ) ;String[ ] parts = name.split ( "/" ) ;name = parts [ parts.length – 1 ] ;BufferedInputStream fis = new BufferedInputStream ( ins ) ;FileOutputStream fos = new FileOutputStream ( name ) ;byte[ ] data = new byte[ BUF_SIZE ] ;int len ;while ( ( len = fis.read ( data, 0, data.length ) ) != -1 )

fos.write ( data, 0, len ) ;fis.close( ) ;fos.close( ) ;

VerifyChecksum( )

static void verifyChecksum ( String origName ) throws Exception

BufferedReader br ;br = new BufferedReader ( new FileReader ( "md5sum.txt" ) ) ;String origSum = br.readLine( ) ;br.close( ) ;String mySum = getChecksum ( origName ) ;if ( origSum.equals ( mySum ) )

S.o.p ( String.format ( "Checksum %1$s is correct", mySum ) ) ;


public static String getChecksum ( String name ) throws Exception

File srcF = new File ( name ) ;DigestInputStream dis = null ;try

MessageDigest m = MessageDigest.getInstance ( "MD5" ) ;dis = new DigestInputStream( new FileInputStream (srcF), m ) ;while ( dis.read( ) != -1 )

;byte[ ] md = m.digest( ) ;StringBuilder sb = new StringBuilder( ) ;for ( byte b : md )

sb.append ( String.format ( "%1$x", b ) ) ;return sb.toString( ) ;

DigestInputStream

FileInputStream

getCheckSum( )

- Read a byte- Update the MD

Resultfinally

if ( dis != null )dis.close( ) ;

Downloading /dl/myfile.zipDownloading /dl/md5sum.txtChecksum 1342cf2d386a84ca8b5a55a3c0bf5fa5 is correctDownloading ftp://quest.ksetindia.com/pub/myftp.zipDownloading ftp://quest.ksetindia.com/pub/md5sum.txtChecksum 1342cf2d386a84ca8b5a55a3c0bf5fa5 is correct

Result


Network SerializationYashavant Kanetkar

[email protected]

Objectives

What is network serialization

How to achieve it programmatically

What is multithreading

When can it be used

How to use it in network serialization

Client Server

Requirement

1C Prog.500.012:45:40

1C Prog.500.012:45:42

1C Prog.500.012:45:44

1C Prog.750.012:45:42

0011 0010 1001 .. Deserialization

1111 0010 1001 .. Serialization


Product Classpackage networking ;import java.util.* ;import java.io.* ;class Product implements Serializable

private int id ; private String Name ;private float price ; transient private Date creationTime ;public Product( )

creationTime = new Date( ) ;System.out.println (" >>Product.constructor1<<" ) ;

public Product ( int num, String name, float p)

creationTime = new Date( ) ;id = num ; Name = name ; price = p ;System.out.println ( " >>Product.constructor2<<" ) ;

public float getPrice( )

return price ;public void setPrice ( float price )

this.price = price ; public String toString( )

return "[ " + String.format ( "%1$tT", creationTime ) + ", " + id + ", " + Name + ", " + price + " ]" ;

private void readObject ( ObjectInputStream in )

throws IOException, ClassNotFoundException

in.defaultReadObject( ) ;this.creationTime = new Date( ) ;

Product Class Cond.

%1 - Postion$t - Print timeT - Only time

Network Serverpackage networking ;import java.net.* ;import java.io.* ;

public class SerializationServer

static public final int portNumber = 10000 ;public SerializationServer( ) throws Exception

ServerSocket lSock = new ServerSocket ( portNumber ) ;Socket cSock = lSock.accept( ) ;ObjectInputStream is = null ;ObjectOutputStream os = null ;try

is = new ObjectInputStream ( cSock.getInputStream( ) ) ;Thread.sleep ( 2000 ) ;Product p = ( Product ) is.readObject( ) ;

Simulates N/Wdelay

ObjectInputStream

InputStream

Listens for a conn. to be madeto this socket & accepts it

Blocking. Creates comm. sckt.

Socket - Bidirectional communication channelEach Sckt has I/O streams to send/rec. dataUse I stream to read data sent by remote m/cUse O stream to send data to remote m/c


Server Continued

S.o.p ( "Server Received : " + p ) ;p.setPrice ( p.getPrice( ) * 1.5f ) ;os = new ObjectOutputStream ( cSock.getOutputStream( ) ) ;os.writeObject ( p ) ;

finally

os.close( ) ;is.close( ) ;cSock.close( ) ;lSock.close( ) ;

ObjectOutputStream

OutputStream

Network Clientpackage networking ;import java.net.* ;import java.io.* ;

public class SerializationClient

static public final int portNumber = 10000 ;public SerializationClient( ) throws Exception

Socket cSock = null ;ObjectOutputStream os = null ;ObjectInputStream is = null ;Product p ;try

cSock = new Socket ( "localhost", portNumber ) ;os = new ObjectOutputStream ( cSock.getOutputStream( ) ) ;

ObjectOutputStream

OutputStream

Client Continuedp = new Product ( 1, "C Prog.", 500.0f ) ;S.o.p ( "Client Sent: " + p ) ;os.writeObject ( p ) ;is = new ObjectInputStream ( cSock.getInputStream( ) ) ;Thread.sleep ( 2000 ) ;p = ( Product ) is.readObject( ) ;System.out.println ( "Server Sent: " + p ) ;

finally

if ( cSock != null )cSock.close( ) ;

if ( os != null )os.close( ) ;


Multiple Units Of Execution

Thread is a unit of executionApps can contain more than one unit (at least one)Once created a thread starts getting time slicesTime slice allocated = Thread QuantumScheduling is done on a per thread basisImproves application's responsivenessSimplify program organization Copying in thread1

Playing AVI file in thread2

Scroll whileDownloading

Check whileTyping

package networking ;import java.io.* ;public class NetSerialTester


Thread serverT ;serverT = new Thread ( new ServerRunner( ) ) ;serverT.start( ) ;Thread.sleep ( 400 ) ;Thread clientT ;clientT = new Thread ( new ClientRunner( ) ) ;clientT.start( ) ;clientT.join( ) ;serverT.join( ) ;

Multithreaded Driver Program

Wait for server thread to bindIn real life S and C run on diff. m/cs

Main T waits for client & server T to terminate

ServerRunner

class ServerRunner implements Runnable

public void run( )

try

new SerializationServer( ) ;catch ( Exception ex )

System.err.println ( ex.getMessage( ) ) ;


ClientRunner

class ClientRunner implements Runnable

public void run( )

try

new SerializationClient( ) ;catch ( Exception ex )

System.err.println ( ex.getMessage( ) ) ;


Zipping / UnzippingYashavant Kanetkar

[email protected]

Objectives

What is zipping & unzipping

Program to

Zip files

List entries in zipped file

Unzip files

ZIP Popular data compression and archival format

A ZIP file contains one or more compressed files

The format was originally designed by Phil Katz for PKZIP

ZIP files generally use the file extensions ".zip" or ".ZIP"

ZIP format compresses every file separately

This allows individual files to be retrieved


RequirementCurrent Directory

/build/dist/nbproject/src/test

buildcartdecencmanifest.MF

s.zip

zipAll( )

showZipEntries( )

/build/dist/nbproject/src/test

buildcartdecenc

if t MF

unzipAll( )

In temp Dir

Programpackage zipunzip ;import java.io.* ;import java.util.* ;import java.util.zip.* ;public class ZipUnzip


ZipOutputStream zos ;zos = new ZipOutputStream ( new FileOutputStream( "s.zip" ));zipAll ( new File ( "." ), zos ) ;zos.close( ) ;showZipEntries ( "s.zip" ) ;File tmpdir = new File ( "temp" ) ;if ( !tmpdir.exists( ) )

tmpdir.mkdir( ) ;unzipAll ( "s.zip", new File(".").getAbsolutePath( ) + "/temp/" ) ;

zipAll( )public static void zipAll ( File f, ZipOutputStream zos )

throws IOException

File[ ] list = f.listFiles( ) ;for ( File ch : list )

if ( !ch.isDirectory( ) )addZipEntry ( zos,

ch.getParent( ) + File.separator + ch.getName( ) ) ;

for ( File ch : list )

if ( ch.isDirectory( ) )zipAll ( ch, zos ) ;


addZipEntry( )

static void addZipEntry ( ZipOutputStream zos, String n )throws IOException

BufferedInputStream fis ;fis = new BufferedInputStream ( new FileInputStream ( n ) ) ;ZipEntry ze = new ZipEntry ( n.replace ( "\\", "/" ) ) ;S.o.p ( ze.getName( ) ) ;zos.putNextEntry ( ze ) ;int count ;byte[ ] data = new byte[ BUF_SIZE ] ;while ( ( count = fis.read ( data, 0, BUF_SIZE ) ) != -1 )

zos.write ( data, 0, count ) ;

- Begins writing a new ZIP file entry- Positions stream to start of entry data

showZipEntries( )

private static void showZipEntries ( String name ) throws Exception

ZipFile zf = new ZipFile ( name ) ;Enumeration <ZipEntry> e ;for ( e = ( Enumeration<ZipEntry> ) zf.entries( ) ;

e.hasMoreElements( ) ; )

ZipEntry ze = e.nextElement( ) ;if ( !ze.isDirectory( ) )

S.o.p ( String.format ( "%1$s %2$d ( %3$d )",ze.getName( ), ze.getCompressedSize( ), ze.getSize( ) ) ) ;

Returns an enumeration of the ZIP file entries

unzipAll( )private static void unzipAll ( String src, String dest )

throws Exception

ZipInputStream zis ;zis = new ZipInputStream ( new FileInputStream ( src ) ) ;ZipEntry e ;while ( ( e = zis.getNextEntry( ) ) != null )

File f = new File ( e.getName( ) ) ;if ( e.isDirectory( ) )

if ( !f.exists( ) )f.mkdirs( ) ;

else

int len ;long size = 0, max = e.getSize( ) ;File parent = new File ( dest + "/" + f.getParent( ) ) ;


if ( !parent.exists( ) )parent.mkdirs( ) ;

FileOutputStream fos ;fos = new FileOutputStream ( dest + "/" + f.getName( ) ) ;byte[ ] data = new byte[ BUF_SIZE ] ;while ( size <= max )

len = zis.read ( data, 0, BUF_SIZE ) ;if ( len == -1 )

break ;fos.write ( data, 0, len ) ;size += len ;

fos.close( ) ;


Multi-threading &Synchronization


Objectives

What is multithreadingHow to get properties of current threadHow to launch multiple threadsPros and cons of different launching methodsNeed for synchronizationHow to achieve it programmatically

t.setName ( "mythread" ) ;S.o.p ( "After name change: " + t ) ;String s = t.getName( ) ;S.o.p ( "Thread name: " + s ) ;

package mainthread ;public class MainThread


Thread t = Thread.currentThread( ) ;

main, 5, mainnameprioritygroup

mythread, 5, main

S.o.p ( "Current thread: " + t ) ;

mythread

Current Thread

Reference to current thread


class Ex extends Thread

package sample ;public class Sample


for ( int i = 0 ; i < 10 ; i ++ ) S.o.p ( "Main thread" ) ;

Ex t = new Ex( ) ;t.start( ) ;

public void run( )

for ( int i = 0 ; i < 10 ; i++ ) S.o.p ( "New thread" ) ;

Launching A Thread

Main threadNew threadNew threadMain threadNew thread:::

Output

Base class Ctor( )Registers thread

with JVMThread's start( ) is called.Signals thread scheduler

New threadbegins execution hereExecution begins only

when the T is scheduled

Multiple Threads

class Ex extends Thread

public class Sample

public static void main ( .. ) throws Exception

for ( int i = 0 ; i < 10 ; i ++ ) S.o.p ( "Main" ) ;

Ex t1 = new Ex( ) ;t1.start( ) ;t1.setName ( "First" ) ;Ex t2 = new Ex( ) ;t2.start ( ) ;t2.setName ("Second" ) ;Ex t3 = new Ex( ) ;t3.start( ) ;t3.setName ( "Third" ) ;

public void run( )

Thread t ; t =Thread.currentThread( ) ;String s = t.getName( ) ;int i ;for ( i = 0 ; i < 10 ; i++ )

S.o.p ( s ) ;

FirstSecondSecondSecondThirdThirdMain:::

t1.join( ) ;t2.join( ) ;t3.join( ) ;

Wait for thisthread to die

class Ex implements Runnable

public class Sample


Thread t = new Thread ( new Ex ( "One" ) ) ;

public void run ( )

int i ;for ( i = 0 ; i < 10 ; i++ )

S.o.p ( str ) ;

String str ;Ex ( String s )

str = s ;


t.start( ) ;

One More Way


Multiple Thread Using Runnablepublic class Sample



Ex t1 = new Thread ( new Ex ( "First" ) ) ;t1.start( ) ;Ex t2 = new Thread ( new Ex ( "Second" ) ) ;t2.start ( ) ;Ex t3 = new Thread ( new Ex ( "Third" ) ) ;t3.start( ) ;

Ex class remains same

Multithreading TipsΩ 2 Methods to launch threads

class that extends Threadclass that implements Runnable

Ω In both cases a thread object must be createdobject ex gets known to Thread

Ω start( ) is a Thread member functionIt registers ex object with scheduler

Ω run( ) must be within our classIt is called by scheduler

Ω extends Thread - Can't use in Multiple Inher. situationΩ extends Thread - Thread related funcs. can be overriden

Requirement

Main Thread

Thread 1 Thread 2

dowork( )

dowork1( ) ;dowork2( ) ;


Programpackage synchtest ;public class SyncTest


Work w = new Work( ) ;Thread t1 = new Thread ( new ThreadRunner ( w ) ) ;Thread t2 = new Thread ( new ThreadRunner ( w ) ) ;t1.start( ) ;t2.start( ) ;t1.join( ) ;t2.join( ) ;

Work Classclass Work

int count = 0 ;public void doWork( ) throws Exception

S.o.p ( String.format ( "(%1$s) ", count ) +Thread.currentThread( ).getName( ) + " : doWork" ) ;

doWork1( ) ; doWork2( ) ;private void doWork1( ) throws Exception

S.o.p ( String.format ( "(%1$s) ", count ) +Thread.currentThread( ).getName( ) + " : doWork1" ) ;

Thread.sleep ( 200 ) ;private void doWork2( ) throws Exception

S.o.p ( String.format ( "(%1$s) ", count ) +Thread.currentThread( ).getName( ) + " : doWork2" ) ;

count ++ ;Thread.sleep ( 100 ) ;

ThreadRunner

class ThreadRunner implements Runnable private Work obj ;public ThreadRunner ( Work o )

obj = o ;public void run( )

for ( int i = 0 ; i < 2 ; i++ )

try

obj.doWork( ) ;catch ( Exception ex )

System.err.println ( ex.getMessage( ) ) ;return ;

(0) Thread-0 : doWork(0) Thread-0 : doWork(0) Thread-1 : doWork(0) Thread-1 : doWork1(0) Thread-0 : doWork2(1) Thread-1 : doWork2(2) Thread-1 : doWork(2) Thread-1 : doWork1(2) Thread-0 : doWork(2) Thread-0 : doWork1(2) Thread-1 : doWork2(3) Thread-0 : doWork2


Solutionsynchronized public void doWork( ) throws Exception

S.o.p ( String.format ( "(%1$s) ", count ) +Thread.currentThread( ).getName( ) + " : doWork" ) ;

doWork1( ) ;doWork2( ) ;

(0) Thread-0 : doWork(0) Thread-0 : doWork1(0) Thread-0 : doWork2(1) Thread-0 : doWork(1) Thread-0 : doWork1(1) Thread-0 : doWork2(2) Thread-1 : doWork(2) Thread-1 : doWork1(2) Thread-1 : doWork2(3) Thread-1 : doWork(3) Thread-1 : doWork1(3) Thread-1 : doWork2


Using Web ServicesYashavant Kanetkar

[email protected]

Objectives

Where are web servicesWhat is WSDLAccessing web services in NetBeansUsing web services programmaticallyCrux of Web Services

Create New Project


Where Is The Web Service?

Names of Functions

WSDL


Add Web Service ClientR

Add WSDL URLhttp://quest.ksetindia.com/CurrencyService/CurrencyService.asmx?WSDL

Java API for XML Web Services


Automatically Generated Classes

Add Code

javax.xml.ws.Service

CurrencyService

CurrencyServiceSoap - Interface

Call methods on remote system

1 US Dollar = 39.325 Indian Rupees

1. Get Conversion Rate

public float getRate ( String from, String to )


2. Countries And Currencies

Output…America (United States) Dollar USD Britain (United Kingdom) Pound GBP Canada Dollar CAD England (United Kingdom) Pound GBP Hong Kong Dollar HKD Hungary Forint HUF India Rupee INR Indonesia Rupiah IDR Iran Rial IRR Iraq Dinar IQD Italy Euro EUR Japan Yen JPY... ... ...... ... ...

Other Methods…

rate = sa.getRateByCountry ( "Australia", "India" ) ;S.o.p ( "1 Australian Dollar = " + rate + " Indian Rupees" ) ;

String curr = sa.getCurrency ( "Hungary" ) ;S.o.p ( "Currency of Hungary is " + curr ) ;

1 Australian Dollar = 36.6099 Indian Rupees

Currency of Hungary is HUF


What Are Web Services

HTTP / HTTPS for data transferXML format for universal acceptanceSOAP – Simple Object Access Protocol

Message envelopeMaps Java types to XML and vice versa

JAX-WS – Java API for XML Web ServicesJAX-RPC – replaces JAX-WS. Is compatible


Using XMLYashavant Kanetkar

[email protected]

Objectives

♦ Different data usage scenarios♦ What is XML♦ How to create XML document, DTD, SAX handler classes♦ How to parse a XML file using SAX handler classes

Data Usage Scenarios

Cas

e I

App101000111010110011

Oracle Ind. SeqApp 101000111010110011

Cas

e II ftpSolaris App Web Server Web Client

Res

Req

Cas

e III

Backup Agent2Backup Agent1

Backup Agent4Backup Agent3Backup

Manager

Cas

e IV

Java App

.NET App COM App


Moral

♦ Need for easy way to describe & exchange data♦ Need for easy way to make function calls in Distributed apps♦ All needs satisfied using XML - Extended Markup Lang.♦ Contains user defined tags (HTML – Std. tags)♦ Sample: <books>

<book><title> VC++ COM and Beyond </title><pages> 460 </pages>

</book><book>

<title> Effective COM </title><pages> 510 </pages>

</book></books>

Tag

XML Reader - Steps Involved

♦ Create new Java application ♦ Project name – Contacts♦ Package - contacts♦ Main Class - XmlContacts

♦ Create new XML file – Contacts.xml♦ Generate DTD file – Contacts.dtd♦ Add its reference in Contacts.xml♦ Generate SAX document handler class♦ Add Contact class♦ Modify SAX handler class♦ Invoke SAX parser and print contacts

Create Contacts.xml

R


Give Filename

Select XML Document Type

Result


Modify Contacts.xml

Create DTD – Contacts.dtd

R

Copy DTD Reference


Paste & Modify

Invoke SAX Document Handler Wizard

R

Step 1 – API Version


Step 2 – Element Mappings

Step 3 – Data Converters

Step 4 – Output Filenames


Create Contact class

package contacts ;public class Contact

private String name ; private String telephone ;public Contact( ) public String getName( )

return name ;public void setName ( String n )

this.name = n ;

public String getTel( )

return telephone ;public void setTel ( String t )

telephone = t ;public String toString( )

return "< " + name + ", "+ telephone + " >" ;

Modify ContactsHandlerImpl

package contacts ;import java.util.ArrayList ;import org.xml.sax.* ;public class ContactsHandlerImpl implements ContactsHandlerArrayList<Contact> list ;Contact current = null ;public void start_Contacts ( final Attributes meta) throws SAXException

list = new ArrayList<Contact>( ) ;public void start_Contact ( final Attributes meta ) throws SAXException

current = new Contact( ) ;

Modification Continuedpublic void handle_Name ( final String data, final Attributes meta)

throws SAXException

current.setName ( data ) ;public void handle_Telephone ( final String data, final Attributes meta )

throws SAXException

current.setTel ( data ) ;public void end_Contact( ) throws SAXException

list.add ( current ) ;public void end_Contacts( ) throws SAXException


Modification Continued

public ArrayList<Contact> getList( )

return list ;protected void finalize( ) throws Throwable

XML Readerpackage contacts ;import java.io.FileReader ;import org.xml.sax.InputSource ;public class XmlContacts


ContactsHandlerImpl handler ;ContactsParser p ;handler = new ContactsHandlerImpl( ) ;p = new ContactsParser ( handler, null ) ;p.parse ( new InputSource (

new FileReader ("src/contacts/Contacts.xml" ) ) ) ;for ( Contact c : handler.getList ( ) )

System.out.println ( c ) ;


Annotations & ReflectionYashavant Kanetkar

[email protected]

Objectives

♦ What are annotations♦ Different scenarios in which it can be used ♦ What is reflection♦ What does it facilitate♦ Writing a Test harness using Annotations & Reflection

Annotations

♦ More mature comments♦ They provide data about a program that is not part of the program itself♦ Annotations can be applied to classes, fields, methods, package♦ 3 uses of annotations:

During CompilationTo detect ErrorsTo suppress warnings

During DeploymentTo generate codeTo create XML files

During ExecutionTo test the program


Error Detection

class base

public void fun ( String s, int i )

System.out.println ( s + i ) ;


@override void fun ( String ss )

Once marked, Error

Annotation

Suppress Warningpackage sample ;

public class Sample


Ex e = new Ex( ) ; e.fun( ) ;

class Ex

@Deprecatedpublic void fun( )

System.out.println ( "Hello" ) ;

Once marked, Warning

Annotation

@SuppressWarnings ( value = "deprecation" )

To suppress Warning

Annotation With Multiple Elements

@Retention ( RetentionPolicy.RUNTIME )@Target ( ElementType.METHOD, ElementType.CLASS )@interface Author

String Company( ) default "KSET Pvt Ltd" ;String Coder( ) ; String Reviewer( ) ;String[ ] Testers( ) ;int VersionNumber default 1.0 ;

Has multiple elements

Annotation - Author

Some have default values

Avlbl at runitme SOURCE, CLASS Won't work for a Field

@Author ( Coder = "Rahul", Reviewer = "Ranjit", Testers = "A", "B" )class Cricket

Usage


Reflection

Get Information Use Information

Create objectModify objectCall methods

Object Class

Fields

InterfaceConstants

CtorsMethods

Superclass

MethodsClass Modifiers

All this at Runtime!

Using @ At Runtimepackage annotationsreflection ;import java.lang.annotation.* ;import java.lang.reflect.* ;

@Retention ( RetentionPolicy.RUNTIME )@Target ( ElementType.METHOD )@interface TestMethod

class ClassUnderTest

@TestMethod public static void testcase1( )

S.o.p ( "testcase1" ) ;@TestMethod public static void testcase2( )

S.o.p ( "testcase2" ) ;throw new RuntimeException ( "testcase2" ) ;

Program Continued

public static void testcase3( )

S.o.p ( "testcase3" ) ;


Test The Class

public class TestHarness


int passed = 0, failed = 0 ;String className = "annotationsreflection.ClassUnderTest" ;for ( Method m : Class.forName ( className ).getMethods( ) )

if ( m.isAnnotationPresent ( TestMethod.class ) )

try

m.invoke ( null ) ; passed++ ;

- For each class a Class object is maintained by JRE- It contains information about the class

Get Class obj

Returns array of Method objects

Call to static method

Program Continued

catch ( Throwable ex )

S.o.p ( "Test %s failed: %s %n", m, ex.getCause( ) ) ;failed++ ;

S.o.p ( "Passed: %d, Failed %d%n", passed, failed ) ;

testcase1testcase2Test public static void annotationsreflection.ClassUnderTest.testcase2() failed: java.lang.RuntimeException: testcase2 Passed: 1, Failed 1

Output

Yashavant Kanetkar [email protected] Solutions Using J2EE / Lecture 01 1 Yashavant...

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