Java Programming

117
1 JAVA Programming Mr.Anjan Mahanta LCCT International Business Studies Program [email protected]

Transcript of Java Programming

Page 1: Java Programming

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JAVA

Programming

Mr.Anjan Mahanta LCCT International Business Studies Program

[email protected]

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About the JAVA Technology

• Java technology is both a programming language and

a platform

• The Java programming language is a high-level

language that can be characterized by all of the

following

– Simple

– Architecture neutral

– Object oriented

– Portable

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About the JAVA Technology

• In the Java programming language, all source code is

first written in plain text files ending with the .java

extension.

• Those source files are then compiled into .class files

by the Java compiler (javac).

• A .class file does not contain code that is native to

your processor; it instead contains bytecodes-- the

machine language of the Java Virtual Machine.

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Concepts of Objects

Name the person(s) who developed Java?

Answer: Java was developed by James

Gosling & Patrick Naughton at Sun

Microsystems, Inc. in 1991.

What was the initial name of Java?

Answer: Java language was initially called

“Oak” and was renamed “Java” in 1995.

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Concepts of Objects

Important features of JAVA.

Java is a platform - independent language

It is highly reliable

It is a distributed language

It is an object oriented language

What kind of files contain Java source code?

Answer: The Java source code is saved in files with

names the end with “.java”.

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Concepts of Objects

What is source code?

Answer: Source code is the plain text that makes up

the part or all of a computer program.

What is bytecode?

Answer: Bytecode is a low-level computer language

translation of Java source code program.

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About the JAVA Technology

• The Java launcher tool (java) then runs your

application with an instance of the Java Virtual

Machine.

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Java compilation process

Java

Program

Java

Compiler

(javac)

Java

Byte Code Can be

executed

MS-DOS

Windows (X)

UNIX

Any other (O.S.)

Source Code Java Virtual

Machine

Platform

Independence

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About the JAVA Technology

• Because the Java Virtual Machine is available on

many different operating systems, the same .class

files are capable of running on

– Microsoft Windows,

– the Solaris TM Operating System (Solaris OS),

– Linux, or

– MacOS.

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1. Concepts of Objects

What is a Java virtual machine?

Answer: A Java virtual machine(JVM) is a software system that translates and executes Java bytecode.

Name two types of Java programs?

Answer: We can develop two types of Java programs

1. Stand-alone application

2. Web applets

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Concepts of Objects

What is an object?

Answer: An object is an identifiable entity with some

characteristics and behavior.

Example:

Object - Person

Variables - First name, Last name, Age, Weight

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Creating your First Application

• Your first application, HelloWorldApp, will simply

display the greeting "Hello world!". To create this

program, you will:

Create a source file. A source file contains text, written in the Java programming language, that you and other programmers can understand. You can use any text editor to create and edit source files.

Compile the source file into a .class file. The Java

compiler, javac, takes your source file and translates its text into instructions that the Java Virtual Machine can understand. The instructions contained within this file are known as bytecodes.

Run the program. The Java launcher (java) uses the Java Virtual Machine to run your application.

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Create a Source File

• First, start your editor. You can launch the NotePad editor from

the Start menu by selecting Programs > Accessories >

NotePad. In a new document, type in the following code:

• /**

• * The HelloWorldApp class implements an application that

• * simply displays "Hello World!" to the standard output.

• */

• class HelloWorldApp {

• public static void main(String[] args) {

• //Display "Hello World!"

• System.out.println("Hello World!");

• }

• }

• You can save the file as HelloWorldApp.java

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Saving a Source File

• You can save the file as HelloWorldApp.java

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Compile the Source File

• Bring up a shell, or "command," window

• You can do this from the Start menu by choosing MS-DOS

Prompt (Windows 95/98) or Command Prompt (Windows

NT/XP), or by choosing Run... and then entering cmd

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Compile and Run

• To Compile the Program, execute the compiler, javac,

specifying the name of the source file on the command line

C:\> javac HelloWorldApp.java

• The java compiler creates a file called HelloWorldApp.class

• To run the program, we must use the Java Interpreter called

Java by,

java HelloWorldApp

• The output is displayed,

Hello World!

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Setting up a project

• Click on NetBeans icon in your desktop

• Choose File > New Project (Ctrl-Shift-N)

• Under Categories, select General

• Under Projects, select Java Class Library

• Click Next

• Under Project Name, enter MyProject1

• Click Finish

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Creating a new program

• Choose File > New Project

• Under Categories, select General

• Under Projects, select Java Application

• Click Next

• Under Project Name, enter Example1

• Click Finish

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Example 1

Type in the following code:

package example1;

public class Main {

/** Creates a new instance of Main */

public Main() {

}

/**

* @param args the command line arguments

*/

public static void main(String[] args) {

// TODO code application logic here

System.out.println("Hello Java");

}

}

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Explanation of the program

• /** Creates a new instance of Main */

• This is a comment

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Explanation of the program

• package example1;

• name of the program

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Explanation of the program

• public static void main(String[ ] args) {

• This line begins the main() method.

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Explanation of the program

• // TODO code application logic here

• This is a single line comment.

• It begins with // and ends at the end of the line.

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Explanation of the program

• System.out.println("Hello Java");

• This line outputs the string “Hello Java” followed by a new line on the screen.

• The println() statement ends with a semicolon.

• All statements in Java end with a semicolon.

• The first } is the program ends main()

• The last } ends the class definition.

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Compiling and Running

• Click on Run in the Menu bar

• Select Run File

• Click on “Run Main.Java”

To save

• Press CTRL+S

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Example 2

package example2;

public static void main(String args[]) {

int num;

num=100;

System.out.println ("This is num: " + num);

num=num * 2;

System.out.print ("The value of num * 2 is ");

System.out.println(num);

}

}

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Example 3 package example3;

public static void main(String args[]) {

int x,y;

x=10;

y=20;

if (x<y) System.out.println(“x is less than y”);

x=x*2;

if (x==y) System.out.println(“x now equal to y”);

x=x+2;

if (x>y) System.out.println(“x now greater than y”);

}

}

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Example 4

package example4;

public static void main(String args[]) {

int x;

for(x=0; x<10; x=x+1)

System.out.println(“This is x:” +x);

}

}

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Lab Assignments

1. Write a program to display the following output

My name is ______

I am ____ years old

I study in IEP2 at LCCT

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Example 5

package example5;

public static void main(String args[]) {

int x,y;

y=20;

for(x=0; x<10; x++) {

System.out.println(“This is x:” +x);

System.out.println(“This is Y:” +y);

y=y-2;

}

}

}

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Seperators

Symbol Name Purpose

( ) Parentheses Used to contain list of

parameters

{ } Braces Used to maintain the

value of arrays

[ ] Brackets Used to declare array type

; Semicolon Terminates statements

, Comma Used to chain statements

together inside a for

statement

. Period Used to separate package

names and variables

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Data Types

• Integers

– This group includes byte, short, int, long which are for whole

valued signed numbers.

• Floating-point numbers

– This group includes float and double, which represent numbers with

fractional precision.

• Characters

– This group includes char, which represents symbols in a character

set, like letters and numbers.

• Boolean

– This group includes boolean, which is a special type for

representing true/false values.

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Integers

Name Width in Bits

long 64

int 32

short 16

byte 8

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Example 6

package example6;

public static void main(String args[]) {

int lightspeed;

long days;

long seconds;

long distance;

lightspeed = 186000;

days=1000; // number of days

seconds=days * 24 * 60 * 60; // convert to seconds

distance=lightspeed * seconds; // compute distance

System.out.print(“In ” + days);

System.out.print(“ days light will travel about ”);

System.out.println(distance + “ miles.”);

}

}

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Floating-Point Types

Name Width in Bits

double 64

float 32

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Example 7

package example7;

public static void main(String args[]) {

double pi, r, a;

r= 10.8; // radius of circle

pi=3.1416; // value of pi

a= pi * r * r; // compute area

System.out.println(“Area of circle is: ” + a);

}

}

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Example 8 (Character)

package example8;

public static void main(String args[]) {

char ch1, ch2;

ch1=88; // code for X

ch2= ‘Y’;

System.out.print (“ch1 and ch2: ”);

System.out.println(ch1 + “ ” +ch2);

}

}

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Example 9 (Character)

package example9;

public static void main(String args[]) {

char ch1;

ch1=‘X’;

System.out.println (“ch1 contains: ” + ch1);

ch1++; // increment ch1

System.out.println(“ch1 is now ” +ch1);

}

}

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Example 10 (Booleans)

package example10;

public static void main(String args[]) {

boolean b;

b = false;

System.out.println(“b is ” +b);

b=true;

System.out.println(“b is ” +b);

}

}

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Example 11

(Dynamic Initialization) package example11;

public static void main(String args[]) {

double a=3.0, b=4.0;

// c is dynamically initialized

double c = Math.sqrt(a*a + b*b);

System.out.println(“Hypotenuse is ” +c);

}

}

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Example12

(Variable life time) package example12;

public static void main(String args[]) {

int x;

for(x=0; x<3; x++) {

int y=-1; // y is initialized each time

System.out.println(“Y is: ” +y); //this always prints -1

y=100;

System.out.println(“Y is now: ” +y);

}

}

}

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Example 13

(Automatic Conversions) package example 13;

public static void main(String args[]) {

byte b;

int i=257;

double d=323.142;

System.out.println(“\nConversion of int to byte.”);

b=(byte) i;

System.out.println(“i and b ” + i + “ ” +b);

System.out.println(“\nConversion of double to int.”);

i=(int) d;

System.out.println(“d and i ” + d + “ ” +i);

System.out.println(“\nConversion of double to byte.”);

b=(byte) d;

System.out.println(“d and b ” + d + “ ” +b);

}

}

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Arrays

• An array is a group of like-typed variables

that are referred to by a common name.

• One-dimensional Arrays

Syntax,

type var-name[];

Example,

int month_days[];

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Example 14

(One-Dimensional Arrays) package example14;

public static void main(String args[]) {

int month_days[];

month_days = new int[12];

month_days[0]=31;

month_days[1]=28;

month_days[2]=31;

month_days[3]=30;

month_days[4]=31;

month_days[5]=30;

month_days[6]=31;

month_days[7]=31;

month_days[8]=30;

month_days[9]=31;

month_days[10]=30;

month_days[11]=31;

System.out.println(“April has” + month_days[3] + “days”);

}

}

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Example 15

(One-Dimensional Arrays) package example15;

public static void main(String args[]) {

int month_days[]={ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

System.out.println(“April has” + month_days[3] + “days”);

}

}

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Example 16

(One-Dimensional Arrays) package example16;

public static void main(String args[]) {

double nums[]={ 10.1, 11.2, 12.3, 13.4, 14.5};

double result = 0;

int i;

for (i=0; i<5; i++)

result = result + nums[i];

System.out.println(“Average is” + result / 5);

}

}

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Example 17

(Two-Dimensional Arrays) package example17;

public static void main(String args[]) {

int twoD[] []= new int [4] [5];

int i, j, k = 0;

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

for (j=0;j<5;j++) {

twoD[i][j] = k;

k++;

}

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

for(j=0; j<5; j++)

System.out.print(twoD[i][j] + “ ”);

System.out.println();

}

}

}

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Example 17

(Two-Dimensional Arrays) package example17;

OUTPUT

0 1 2 3 4

5 6 7 8 9

10 11 12 13 14

15 16 17 18 19

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Example 18

(Two-Dimensional Arrays) package example18;

public static void main(String args[]) {

int twoD[] []= new int [4] [ ];

twoD[0] = new int [1];

twoD[1] = new int [2];

twoD[2] = new int [3];

twoD[3] = new int [4];

int i,j,k=0;

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

for(j=0; j<i+1; j++) {

twoD[i][j]=k;

k++;

}

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

for(j=0; j<i+1; j++)

System.out.print (twoD[i][j] + “ ”);

System.out.println();

}

}

}

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Example 18

(Two-Dimensional Arrays) package example18;

OUTPUT

0

1 2

3 4 5

6 7 8 9

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Example 19

(Two-Dimensional Arrays) package example19;

public static void main(String args[]) {

double m[] []= {

{ 0*0, 1*0, 2*0, 3*0 },

{ 0*1, 1*1, 2*1, 3*1 },

{ 0*2, 1*2, 2*2, 3*2 },

{ 0*3, 1*3, 2*3, 3*3 }

};

int i,j;

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

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

System.out.print(m[i][j] + “ ”);

System.out.println();

}

}

}

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Example 19

(Two-Dimensional Arrays) package example19;

OUTPUT

0.0 0.0 0.0 0.0

0.0 1.0 2.0 3.0

0.0 2.0 4.0 6.0

0.0 3.0 6.0 9.0

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Example 20

(Three-Dimensional Arrays) package example20;

public static void main(String args[]) {

int threeD[][][]= new int [3][4][5];

int i,j,k;

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

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

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

threeD[i][j][k]=i*j*k;

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

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

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

System.out.print (threeD[i][j][k] + “ ”);

System.out.println();

}

System.out.println();

}

}

}

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Example 20

(Three-Dimensional Arrays) package example20;

OUTPUT

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

0 1 2 3 4

0 2 4 6 8

0 3 6 9 12

0 0 0 0 0

0 2 4 6 8

0 4 8 12 16

0 6 12 18 24

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Arithmetic Operators

Operator Result

+ Addition

- Subtraction

* Multiplication

/ Division

% Modulus

++ Increment

+= Addition assignment

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Arithmetic Operators

Operator Result

-= Subtraction assignment

*= Multiplication assignment

/= Division assignment

%= Modulus assignment

-- Decrement

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Example 21

(Arithmetic Operators) package example21;

public static void main(String args[]) {

System.out.println (“Integer Arithmetic”);

int a=1+1;

int b=a*3;

int c=b/4;

int d=c-a;

int e=-d;

System.out.println (“a= ” +a);

System.out.println (“b= ” +b);

System.out.println (“c= ” +c);

System.out.println (“d= ” +d);

System.out.println (“e= ” +e);

System.out.println(“\n Floating Point Arithmetic”);

double da=1+1;

double db=da*3;

double dc=db / 4;

double dd=dc-a;

double de=-dd;

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Example 21

(Arithmetic Operators)

System.out.println (“da= ” +da);

System.out.println (“db= ” +db);

System.out.println (“dc= ” +dc);

System.out.println (“dd= ” +dd);

System.out.println (“de= ” +de);

}

}

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Example 22

(Modulas Operator)

• The modulus operator, % returns the remainder of a division operator.

package example22;

public static void main(String args[]) {

int x= 42;

double y=42.25;

System.out.println (“x mod 10= ” + x % 10);

System.out.println (“y mod 10= ” + y % 10);

}

}

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Example 23 (Arithmetic Assignment Operator)

package example23;

public static void main(String args[]) {

int a=1;

int b=2;

int c=3;

a+=5;

b*=4;

c+=a*b;

c%=6;

System.out.println(“a = ” + a);

System.out.println(“b = ” + b);

System.out.println(“c = ” + c);

}

}

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Example 24 (Increment & Decrement)

package example24;

public static void main(String args[]) {

int a=1;

int b=2;

int c;

int d;

c= ++b;

d=a++;

c++;

System.out.println(“a = ” + a );

System.out.println(“b = ” + b );

System.out.println(“c = ” + c );

System.out.println(“d = ” + d );

}

}

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Relational & Logical Operators

Operator Result

== Equal to

!= Not equal to

> Greater than

< Less than

>= Greater than or equal to

<= Less than or equal to

& Logical AND

| Logical OR

?: Ternary if-then-else

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Example 25 (The ? Operator)

Syntax:

expression1 ? Expression 2 : Expression 3

package example25;

public static void main(String args[]) {

int i,k;

i=10;

k=i<0 ? -i: i;

System.out.println(“i = ” + k );

}

}

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Control Statements

• If is used to route program execution through two different paths.

Syntax:

if (condition) statement1;

else statement2;

Example:

int a,b;

if (a<b) a=0;

else

b=0;

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IF Statement

Example 26 package example26;

public static void main(String args[]) {

int i,k;

i=10;

k=20;

if (i<k) System.out.println(“i is less than k” );

else System.out.println(“k is less than i”);

}

}

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Nested IF Statement

package example27;

public static void main(String args[]) {

int month = 4;

String season;

if (month == 12 || month == 1 || month == 2)

season=“Winter”;

else if (month == 3 || month == 4 || month == 5)

season=“Spring”;

else if (month == 6 || month == 7 || month == 8)

season=“Summer”;

else if (month == 9 || month == 10 || month == 11)

season=“Autumn”;

else

season=“Bogus Month”;

System.out.println(“April is in the ” + season + “.” );

}

}

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Switch Case

package example28;

public static void main(String args[]) {

int month = 4;

String season;

switch (month) {

case 12:

case 1:

case 2:

season=“Winter”;

break;

case 3:

case 4:

case 5:

season=“Spring”;

break;

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Switch Case

case 6:

case 7:

case 8:

season=“Summer”;

break;

case 9:

case 10:

case 11:

season=“Autumn”;

break;

default:

season=“Bogus Season”;

}

System.out.println(“April is in the ” + season + “.” );

}

}

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Input Example 1

• Write a program to input a number and

check whether this number is even or odd.

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Code

Example 1 import java.io.*;

public static void main(String s[]) throws IOException{

int n;

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

System.out.println("Enter number");

String x=I.readLine();

n=Integer.parseInt(x);

if(n%2==0)

System.out.println("Even number");

else

System.out.println("Odd number");

}

}

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Input Example 2

• Write a program to input a letter and check

whether this letter is vowel or consonant.

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Code

Example 2 import java.io.*;

public static void main(String s[])throws IOException {

char c;

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

System.out.println("Enter a letter: ");

c=(char)I.read();

if (c=='a' || c=='e' ||c=='i'||c=='o'||c=='u' )

System.out.println("Vowel");

else

System.out.println("Consonant");

}

}

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Input Example 3

• Write a program to input three numbers

and print the highest number.

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Code

Example 3 import java.io.*;

public static void main(String s[])throws IOException {

int a,b,c,max;

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

System.out.println ("Enter three numbers");

String s1=I.readLine();

String s2=I.readLine();

String s3=I.readLine();

a=Integer.parseInt(s1);

b=Integer.parseInt(s2);

c=Integer.parseInt(s3);

if(a>b && a>c)

max=a;

else if(b>a && b>c)

max=b;

else

max=c;

System.out.println("Maximum Number= " +max);

}

}

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Input Example 4

• Write a program to input three numbers

and print the numbers in ascending order. First number = 7

Second number = 3

Third number = 5

Output

3

5

7

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Code 4.1

import java.io.*;

public static void main(String s[])throws IOException {

int a,b,c,max,mid,min;

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

System.out.println("Enter three numbers: ");

String s1=I.readLine();

String s2=I.readLine();

String s3=I.readLine();

a=Integer.parseInt(s1);

b=Integer.parseInt(s2);

c=Integer.parseInt(s3);

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Code 4.2

if(a>b)

{

if(b>c)

{

max=a;

mid=b;

min=c;

}

else

{

max=a;

mid=c;

min=b;

}

System.out.println( +min);

System.out.println(+mid);

System.out.println(+max);

}

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Code 4.3

else if(b>c)

{

if(c>a)

{

max=b;

mid=c;

min=a;

}

else

{

max=b;

mid=a;

min=c;

}

System.out.println( +min);

System.out.println(+mid);

System.out.println(+max);

}

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Code 4.4

else if(c>a)

{

if(a>b)

{

max=c;

mid=a;

min=b;

}

else

{

max=c;

mid=b;

min=a;

}

System.out.println( +min);

System.out.println(+mid);

System.out.println(+max);

}

}

}

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80

For…Loop

• For_Example1

• Write a program to print your name n

number of times.

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Code

import java.io.*;

public static void main(String s[]) throws IOException{

int n,i;

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

System.out.println("Enter how many times? ");

String x=I.readLine();

n=Integer.parseInt(x);

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

{

System.out.println(“Your name”);

}

}

}

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• For_Example2

• Write a program to enter n numbers and

display their sum.

How many numbers? 3

Enter number 1 5

Enter number 2 10

Enter number 3 5

Sum = 20

Page 83: Java Programming

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Code

import java.io.*;

public static void main(String s[]) throws IOException{

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

int i,n,sum,num;

sum=0;

System.out.println("Enter how many numbers");

String x=I.readLine();

n=Integer.parseInt(x);

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

{

System.out.println("Enter number "+ i );

num=Integer.parseInt(I.readLine());

sum=sum+num;

}

System.out.println("Sum= "+sum);

}

}

Page 84: Java Programming

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• For_Example3

• Write a program to find the sum of the

following series:

12 + 32 + 52 +………+ upto nth terms.

Page 85: Java Programming

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Code

import java.io.*;

public static void main(String s[]) throws IOException{

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

int i,n,sum,sq;

sum=0;

System.out.println("Enter the nth term: ");

String x=I.readLine();

n=Integer.parseInt(x);

for(i=1;i<=n;i=i+2)

{

sq=i*i;

sum=sum+sq;

}

System.out.println("Sum= "+sum);

}

}

Page 86: Java Programming

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String Function

substring() substring(int beginIndex)

• Returns a new string that is a substring of

this string.

Page 87: Java Programming

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String Handling

• 5.1

• Write a program to enter a string and print

this string in reverse order

• Example:

lampang

gnapmal

Page 88: Java Programming

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String Handling

Example 5.1

import java.io.*;

public static void main(String s[])throws IOException {

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

int i,l;

System.out.println("Enter a string");

String str=I.readLine();

l=str.length();

for(i=l-1;i>=0;i--)

{

System.out.print(str.substring(i,i+1));

}

}

}

Page 89: Java Programming

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String Handling

• 5.2

• Write a program to enter a string and print

initial character of each word of the string.

• Example:

input: Read Only Memory

output: ROM

Page 90: Java Programming

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String Handling

Example 5.2 import java.io.*;

public static void main(String s[])throws IOException {

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

String str;

int i,l;

System.out.println("Enter a string");

str=I.readLine();

str=" " + str;

l=str.length();

for(i=0;i<=l-1;i++)

{

if(str.charAt(i)==' ')

{

System.out.print(str.charAt(i+1));

}

}

}

}

Page 91: Java Programming

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String Handling

• 5.3

• Write a program to enter a string print it in the following format.

• Example:

input: HELLO

output:

H

H E

H E L

H E L L

H E L L O

Page 92: Java Programming

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String Handling

Example 5.3 import java.io.*;

public static void main(String s[])throws IOException {

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

String str;

int i,l,j;

System.out.println("Enter a string");

str=I.readLine();

l=str.length();

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

{

System.out.print(str.substring(0,i));

}

}

}

Page 93: Java Programming

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String Handling

• 5.4

• Write a program to enter a string print it in the following format.

• Example:

input: HELLO

output:

H E L L O

H E L L

H E L

H E

H

Page 94: Java Programming

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String Handling

Example 5.4 import java.io.*;

public static void main(String s[])throws IOException {

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

String str;

int i,l,j;

System.out.println("Enter a string");

str=I.readLine();

l=str.length();

for(i=l;i>=1;i--)

{

System.out.print(str.substring(0,i));

}

}

}

Page 95: Java Programming

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String Handling

• 5.5

• Write a program to enter a string print it in the following format.

• Example:

input: HELLO

output:

H E L L O

E L L O

L L O

L O

O

Page 96: Java Programming

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String Handling

Example 5.5 import java.io.*;

public static void main(String s[])throws IOException {

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

String str;

int i,l,j;

System.out.println("Enter a string");

str=I.readLine();

l=str.length();

for(i=0;i<=l-1;i++)

{

System.out.print(str.substring(i,5));

}

}

}

Page 97: Java Programming

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String Handling

• 5.6

• Write a program to enter a string print it in the following format.

• Example:

input: HELLO

output:

O

L O

L L O

E L L O

H E L L O

Page 98: Java Programming

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String Handling

Example 5.6 import java.io.*;

public static void main(String s[])throws IOException {

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

String str;

int i,l,j;

System.out.println("Enter a string");

str=I.readLine();

l=str.length();

for(i=l-1;i>=0;i--)

{

System.out.print(str.substring(i,5));

}

}

}

Page 99: Java Programming

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Review

Enter how many subjects? 3

Enter marks in subject1: 90

Enter marks in subject2: 60

Enter marks in subject3: 80

Grade = 3

Page 100: Java Programming

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Solution

public static void main(String s[])throws IOException {

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

int i,n,num,sum,grade,gpa;

sum=0;

System.out.println("Enter how many subjects: ");

String x =I.readLine();

n=Integer.parseInt(x);

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

{

System.out.println("Enter marks of subject " + i + ": ");

num=Integer.parseInt(I.readLine());

sum=sum+num;

}

Page 101: Java Programming

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Solution

gpa= sum / n;

if (gpa >=80 && gpa<=100)

grade=4;

else if

(gpa >=70 && gpa <= 79)

grade=3;

else if

(gpa >=60 && gpa <=69)

grade=2;

else if

(gpa >=50 && gpa <=59)

grade=1;

else

grade=0;

System.out.println("Grade= " + grade);

}

}

Page 102: Java Programming

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Exercise - 1

• Write a program to enter the monthly

salary and display the income tax with the

help of following table

Monthly Salary Income Tax

7,499 baht or less 20 % of monthly salary

7,500 – 9,999 30 % of monthly salary

10,000 or more 40 % of monthly salary

Page 103: Java Programming

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Exercise - 2

*** MENU ***

1.To find area of rectangle

2. To find area of circle

3. To find area of square

Enter your choice: 1

Enter length & width ?

Area of rectangle=?

Page 104: Java Programming

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Exercise - 2

*** MENU ***

1.To find area of rectangle

2. To find area of circle

3. To find area of square

Enter your choice: 2

Enter radius of circle ?

Area of circle=?

Page 105: Java Programming

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Exercise - 2

*** MENU ***

1.To find area of rectangle

2. To find area of circle

3. To find area of square

Enter your choice: 3

Enter side of square ?

Area of square=?

Page 106: Java Programming

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Solution

public static void main(String s[]) throws IOException

{

InputStreamReader R= new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

int ch,l,w,side,arrect,arsq;

double r,arcir;

compute ob=new compute();

System.out.println(" *** MENU *** ");

System.out.println("1.To find area of rectangle");

System.out.println("2. To find area of circle");

System.out.println("3. To find area of square");

System.out.println("Enter your choice:");

ch=Integer.parseInt(I.readLine());

Page 107: Java Programming

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Solution

switch(ch)

{

case 1:

{

System.out.print("Enter length & width");

l=Integer.parseInt(I.readLine());

w=Integer.parseInt(I.readLine());

arrect=ob.area(l,w);

System.out.print("Area of rectangle=" + arrect);

break;

}

Page 108: Java Programming

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Solution

case 2:

{

System.out.print("Enter radius of circle");

r=Double.parseDouble(I.readLine());

arcir=ob.area(r);

System.out.print("Area of circle =" +arcir);

break;

}

case 3:

{

System.out.print("Enter side of square");

side=Integer.parseInt(I.readLine());

arsq=ob.area(side);

System.out.print("Area of square=" +arsq);

break;

}

default:

System.out.print("Invalid choice");

}

}

}

Page 109: Java Programming

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Exercise

Enter how many numbers? 3

Enter number 1: 5

Enter number 2: 7

Enter number 3: 2

Minimum number = 2

Maximum number = 7

Page 110: Java Programming

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Solution

public static void main(String s[]) throws IOException {

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

int n,num,i,max,min,sum,avg;

max=0;

min=100;

sum=0;

System.out.println("Enter how many numbers: ");

String x =I.readLine();

n=Integer.parseInt(x);

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

{

System.out.println("Enter number " + i + ": ");

num=Integer.parseInt(I.readLine());

Page 111: Java Programming

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Solution

sum=sum+num;

if (num > max)

max=num;

else

max=max;

if (num<min)

min=num;

else

min=min;

}

avg=sum/n;

System.out.println("Maximum Number :" +max);

System.out.println("Minimun Number :" +min);

System.out.println(“Average Number :” +avg);

}

}

Page 112: Java Programming

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Exercise

Enter how many products: 2

Enter product price 1:$ 50

Enter product price 2:$ 50

Enter discount % :$ 10

Total Price =$ 90

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public static void main(String s[]) throws IOException {

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

int n,i,sum,num,d;

sum=0;

System.out.println("Enter how many products: ");

String x =I.readLine();

n=Integer.parseInt(x);

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

{ System.out.println("Enter product price " + i + ": ");

num=Integer.parseInt(I.readLine());

sum=sum+num;

} System.out.println("Enter discount % :");

String y =I.readLine();

d=Integer.parseInt(y);

sum= sum-(sum*d/100);

System.out.println("Total Price =" + sum);

}

}

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public static void main(String s[]) throws IOException {

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

int n,i,m;

System.out.println("Enter number: ");

String x =I.readLine();

n=Integer.parseInt(x);

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

{

m=i*n;

System.out.println(n + "*"+ i + "=" +m);

}

}

}

Page 115: Java Programming

115

Exercise

Enter number1: 2

Enter number2: 2

** Select Operation **

** a add(+) ** ** s sub(-) **

** m mul(*) **

** d div(/) **

Enter your choice: a

Addition of 2 + 2 = 4

Page 116: Java Programming

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Solution

public static void main(String s[]) throws IOException {

InputStreamReader R=new InputStreamReader (System.in);

BufferedReader I=new BufferedReader(R);

int n,i,m,add;

char c;

System.out.println("Enter number1: ");

String x =I.readLine();

n=Integer.parseInt(x);

System.out.println("Enter number2: ");

String y=I.readLine();

m=Integer.parseInt(y);

Page 117: Java Programming

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System.out.println("Select Operation");

System.out.println("a. add(+)");

System.out.println("s. sub(-)");

System.out.println("m. mul(*)");

System.out.println("d. div(/)");

System.out.println("Enter your choice");

c=(char)I.read();

switch(c)

{

case 'a':

{

add=n+m;

System.out.println("Addition ="+ add);

}

default:

System.out.print("Invalid choice");

}

}

}