Java slides

7/24/2019 Java slides

1/64

1Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

Chapter 3 Control Statements

Chapter 1 Introduction to Computers, Programs,and Java

Chapter 2 Primitive Data Types and Operations

Chapter !oops

Chapter " #rrays

Chapter $ %ethods

&asic computer s'ills such as using (indo)s,

Internet *+plorer, and %icrosot (ord

--1./101./3 in Chapter 1. ecursion

Chapter 23 #lgorithm *iciency and Sorting

Chapter 3 Selection Statements


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OectivesTo declare oolean type and )rite &oolean e+pressions 4-3/25/

To distinguish et)een conditional and unconditional 66 and 77operators 4-3/2/15/

To use &oolean e+pressions to control selection statements 4-3/30

3/$5/

To implement selection control using i and nested i statements4-3/35/

To implement selection control using s)itch statements 4-3/5/

To )rite e+pressions using the conditional operator 4-3/$5 /

To display ormatted output using the System/out/print methodand to ormat strings using the String/ormat method 4-3/"5/

To 'no) the rules governing operand evaluation order, operator

precedence, and operator associativity 4--3/803/95 /


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The booleanType and Operators

Oten in a program you need to compare t)ovalues, such as )hether i is greater than / Java

provides si+ comparison operators 4also 'no)n

as relational operators5 that can e used to

compare t)o values/ The result o the

comparison is a &oolean value: true or alse/

boolean b = (1 > 2);


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Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

Comparison Operators

Operator Name

< less than

greater than

>= greater than or e;ual to

== e;ual to

!= not e;ual to


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$Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

&oolean Operators

Operator Name

! not

&& and|| or

^ e+clusive or


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"Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

Truth Tale or Operator Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rig

hts reserved. 0!"#!222"$%!&

*+amples

System/out/println4AIs A B num B A divisile y 2 and 3 A B

44num 2 ?? >5 66 4num 3 ?? >555E

System/out/println4AIs A B num B A divisile y 2 or 3 A B 44num 2 ?? >5 77 4num 3 ?? >555E

System/out/println4AIs A B num B

A divisile y 2 or 3, ut not oth A B

44num 2 ?? >5 @ 4num 3 ?? >555E


11/6411Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rig


*+ample: Determining !eap Fear

LeapYearLeapYear RunRun

This program irst prompts the user to enter a year as

an int value and chec's i it is a leap year/

# year is a leap year i it is divisile y ut not y

1>>, or it is divisile y >>/

4year ?? >66 year 1>>


12/6412Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rig


*+ample: # Simple %ath !earning Tool

AdditionTutorAdditionTutor RunRun

This e+ample creates a program to let a irst grader practice additions/The program randomly generates t)o single0digit integers numer1

and numer2 and displays a ;uestion such as G(hat is 8 B .H to the

student, as sho)n elo)/ #ter the student types the ans)er in the

input dialog o+, the program displays a message dialog o+ to

indicate )hether the ans)er is true or alse/
http://html/LearnAddition.htmlhttp://var/www/apps/conversion/tmp/scratch_3/html%5CLearnAddition.bathttp://var/www/apps/conversion/tmp/scratch_3/html%5CLearnAddition.bathttp://var/www/apps/conversion/tmp/scratch_3/html%5CLearnAddition.bathttp://html/LearnAddition.htmlhttp://html/LearnAddition.html


13/6413Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

The 6 and 7 Operators

&&: conditional AND operator

&: unconditional AND operator

||: conditional OR operator

|: unconditional OR operator

exp1 && exp2

(1 < x) && (x < 100)

(1 < x) & (x < 100)



The 6 and 7 Operators

If x is 1, what is x after this

expression

(x > 1) & (x < 1")

If x is 1, what is x after this

expression

(1 > x) && ( 1 > x)

#ow about (1 == x) | (1" > x)

(1 == x) || (1" > x)


15/641$Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

Selection Statements

ifStatements

swit$hStatements

Conditional Operators


16/641"Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

SimpleifStatements

&oolean

*+pression

true

Statement4s5

alse4radius =? >5

true

area ? radius radius PIE

System/out/println4AThe area or the circle o A B

Aradius A B radius B A is A B area5E

alse

4#5 4&5

i 4oolean*+pression5 statement4s5E

K

i 4radius =? >5

area ? radius radius PIE System/out/println4AThe areaA

B A or the circle o radius A

B radius B A is A B area5E

K



Lote

if ((i > ") && (i < 1"))%

'steoutprintln(*i is an * !

! *inte+er between " an, 1"*);

-

4a5

*;uivalent

45

if ((i > ") && (i < 1"))

'steoutprintln(*i is an * !

! *inte+er between " an, 1"*);

Outer parentheses re;uired &races can e omitted i the loc' contains a single

statement



Caution

#dding a semicolon at the end o an i clause is a common

mista'e/i 4radius =? >5E

area ? radiusradiusPIE

System/out/println4

AThe area or the circle o radius A B

radius B A is A B area5E

KThis mista'e is hard to ind, ecause it is not a compilation error

or a runtime error, it is a logic error/

This error oten occurs )hen you use the ne+t0line loc' style/

(rong


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2>Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

ifelse*+ample

if (raius >= ") %area = raius 0 raius 0 1134;

'steoutprintln(*5he area for the 6

6$ir$le of raius * raius * is * area);

-

else %

'steoutprintln(*7e+ati8e input*);

-


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%ultiple #lternative i Statements

if (s$ore >= 4"")+ra,e = 9:9;

else

if (s$ore >= "")

+ra,e = 99;

else

if (s$ore >= "")

+ra,e = 99;

else

if (s$ore >= ?"")

+ra,e = 9@9;

else

+ra,e = 9A9;

*;uivalent

if (s$ore >= 4"")

+ra,e = 9:9;

else if (s$ore >= "")

+ra,e = 99;

else if (s$ore >= "")

+ra,e = 99;

else if (s$ore >= ?"")

+ra,e = 9@9;

else

+ra,e = 9A9;

aniation


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Trace i0else statement

i 4score =? .>/>5

grade ? M#ME

else i 4score =? 9>/>5

grade ? M&ME

else i 4score =? 8>/>5 grade ? MCME

else i 4score =? ">/>5

grade ? MDME

else grade ? MNME

Suppose score is 8>/> The condition is alse

aniation

aniation


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i 4score =? .>/>5

grade ? M#ME


grade ? M&ME



grade ? MDME

else grade ? MNME

Suppose score is 8>/> The condition is alse

aniation

aniation


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i 4score =? .>/>5

grade ? M#ME


grade ? M&ME



grade ? MDME

else grade ? MNME

Suppose score is 8>/> The condition is true

aniation

aniation


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2$Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&


i 4score =? .>/>5

grade ? M#ME


grade ? M&ME



grade ? MDME

else grade ? MNME

Suppose score is 8>/> grade is C

aniation

aniation


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2"Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&


i 4score =? .>/>5

grade ? M#ME


grade ? M&ME



grade ? MDME

else grade ? MNME

Suppose score is 8>/> *+it the i statement

aniation


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LoteThe else clause matches the most recent i clause in the same

loc'/int i = 1;

int B = 2;

int C = ;

if (i > B)

if(i > C)'steoutprintln(*:*);

else

'steoutprintln(**);

4a5

*;uivalent

4b5

int i = 1;

int B = 2;

int C = ;

if (i > B)

if(i > C)'steoutprintln(*:*);

else

'steoutprintln(**);


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Lote, cont/

Lothing is printed rom the preceding statement/ To orce

the else clause to match the irst i clause, you must add apair o races:

int i = 1;

int B = 2;

int C = ;

if (i > B) {

if (i > C)

'steoutprintln(*:*);

}

else

'steoutprintln(**);

This statement prints &/


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2.Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

TIP

if (nuber D 2 == ")e8en = true;

else

e8en = false;

4a5

*;uivalent boolean e8en= nuber D 2 == ";

45


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3>Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

C#TIOL

if (e8en == true)&'steoutprintln(

*It is e8en*);

4a5

*;uivalent if (e8en)&'steoutprintln(

*It is e8en*);

45


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*+ample: Computing Ta+es

The S ederal personal income ta+ is calculated ased on

the iling status and ta+ale income/ There are our ilingstatuses: single ilers, married iling ointly, married iling

separately, and head o household/ The ta+ rates or 2>>2

are sho)n in Tale 3/1/


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*+ample: Computing Ta+es, cont/

!oputeTax"it#$election$tateent!oputeTax"it#$election$tateent Run

if (status == ") %

EE opute tax for sin+le filers

-

else if (status == 1) %

EE opute tax for arrie file Bointl'-

else if (status == 2) %

EE opute tax for arrie file separatel'

-

else if (status == ) %

EE opute tax for hea of househol

-

else %

EE @ispla' wron+ status

-
http://html/ComputeTaxWithSelectionStatement.htmlhttp://html/ComputeTaxWithSelectionStatement.htmlhttp://var/www/apps/conversion/tmp/scratch_3/html%5CComputeTax.bathttp://html/ComputeTaxWithSelectionStatement.htmlhttp://html/ComputeTaxWithSelectionStatement.htmlhttp://var/www/apps/conversion/tmp/scratch_3/html%5CComputeTax.bathttp://var/www/apps/conversion/tmp/scratch_3/html%5CComputeTax.bathttp://var/www/apps/conversion/tmp/scratch_3/html%5CComputeTax.bathttp://html/ComputeTaxWithSelectionStatement.htmlhttp://html/ComputeTaxWithSelectionStatement.html


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*+ample: #n Improved %ath !earning Tool

This e+ample creates a program to teach a irst grade child

ho) to learn sutractions/ The program randomlygenerates t)o single0digit integers numer1 and numer2)ith numer1 = numer2 and displays a ;uestion such asG(hat is . 2H to the student, as sho)n in the igure/#ter the student types the ans)er in the input dialog o+,the program displays a message dialog o+ to indicate)hether the ans)er is correct, as sho)n in igure/

$u%tractionTutor$u%tractionTutor Run
http://html/SubtractionTutor.htmlhttp://var/www/apps/conversion/tmp/scratch_3/html%5CSubtractionTutor.bathttp://var/www/apps/conversion/tmp/scratch_3/html%5CSubtractionTutor.bathttp://html/SubtractionTutor.htmlhttp://html/SubtractionTutor.html


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*+ample: Quessing &irth Date

ue''irt#Dateue''irt#Date Run

The program can guess your irth date/ unto see ho) it )or's/
http://html/GuessBirthDate.htmlhttp://var/www/apps/conversion/tmp/scratch_3/html%5CGuessBirthDate.bathttp://var/www/apps/conversion/tmp/scratch_3/html%5CGuessBirthDate.bathttp://html/GuessBirthDate.htmlhttp://html/GuessBirthDate.html


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3$Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

swit$hStatementss)itch 4status5

case >: compute ta+es or single ilersE rea'E

case 1: compute ta+es or married ile ointlyE

rea'E

case 2: compute ta+es or married ile separatelyE

rea'E

case 3: compute ta+es or head o householdE

rea'E

deault: System/out/println4A*rrors: invalid statusA5E

System/e+it4>5E

K


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3"Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

swit$hStatement Nlo) Chart

status is >Compute ta+ or single ilers rea'

Compute ta+ or married ile ointly rea'

status is 1

Compute ta+ or married ile separatly rea'status is 2

Compute ta+ or head o household rea'

status is 3

Deault actionsdeault

Le+t Statement

i h St t t l


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swit$hStatement ules

s)itch 4s)itch0e+pression5 case value1: statement4s51E

rea'E

case value2: statement4s52E

rea'E

R

case valueL: statement4s5LE

rea'E

deault: statement4s50or0deaultE

K

The s)itch0e+pression mustyield a value o char, yte,

short, or int type and mustal)ays e enclosed in

parentheses/

The value1, ///, and valueL must

have the same data type as thevalue o the s)itch0e+pression/

The resulting statements in the

case statement are e+ecuted )hen

the value in the case statement

matches the value o the s)itch0

e+pression/ Lote that value1, ///,and valueL are constant

e+pressions, meaning that they

cannot contain variales in the

e+pression, such as 1 B +/

it h St t t l


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swit$hStatement ules

The 'ey)ord rea' is optional,

ut it should e used at the end o

each case in order to terminate the

remainder o the s)itch statement/

I the rea' statement is not

present, the ne+t case statement

)ill e e+ecuted/

s)itch 4s)itch0e+pression5 case value1: statement4s51E

rea'E

case value2: statement4s52E

rea'E

R

case valueL: statement4s5LE

rea'E

deault: statement4s50or0deaultE

K

The deault case, )hich is

optional, can e used to perorm

actions )hen none o the

speciied cases matches thes)itch0e+pression/ The case statements are e+ecuted in se;uential

order, ut the order o the cases 4including the

deault case5 does not matter/ o)ever, it is good

programming style to ollo) the logical se;uence o

the cases and place the deault case at the end/

aniation


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3.Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

Trace s)itch statement

switch($h) %

case9a9F 'steoutprintln($h);

case9b9F 'steoutprintln($h); case9$9F 'steoutprintln($h);

-

Suppose ch is MaM:

aniation


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>Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&


switch($h) %



-

ch is MaM:

aniation


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switch($h) %



-

*+ecute this line

aniation


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switch($h) %



-

*+ecute this line

aniation


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switch($h) %



-

*+ecute this line

aniation


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Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&


switch($h) %



-

Le+t statementE

*+ecute ne+t statement

aniation


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switch($h) %


break; case9b9F 'steoutprintln($h);

breakE

case9$9F 'steoutprintln($h);

-

Suppose ch is MaM:

aniation


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"Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&


switch($h) %



breakE


-

ch is MaM:

aniation


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switch($h) %



breakE


-

*+ecute this line

aniation


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switch($h) %



breakE


-

*+ecute this line

aniation


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.Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&


switch($h) %



breakE


-

Le+t statementE

*+ecute ne+t statement

C di i l O


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$>Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

Conditional Operator

i 4+ = >5

y ? 1else

y ? 01E

is e;uivalent to

y ? 4+ = >5 1 : 01E4oolean*+pression5 e+pression1 : e+pression2

Ternary operator&inary operatornary operator


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$1Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

Conditional Operator

if (nu D 2 == ")

'steoutprintln(nu 6is e8enG);

else

'steoutprintln(nu 6is oG);

'steoutprintln(

(nu D 2 == ") nu 6is e8enG F nu 6is oG);


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Conditional Operator, cont/

(boolean.xp) exp1 F exp2

N tti O t tJD 1/$


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Normatting Output

se the ne) JD 1/$ print statement/

System/out/print4ormat, items5E

(here ormat is a string that may consist o sustrings and

ormat speciiers/ # ormat speciier speciies ho) an item

should e displayed/ #n item may e a numeric value,

character, oolean value, or a string/ *ach speciier egins

)ith a percent sign/

Neature

N tl d S ii

JD 1/$


54/64


Nre;uently0sed SpeciiersNeature

Specifier Output Example

Db a boolean 8alue true or false

D$ a $hara$ter 9a9

D a e$ial inte+er 2""

Df a floatin+/point nuber 3?""""

De a nuber in stanar s$ientifi$ notation 33?"""e"1

Ds a strin+ *Ha8a is $ool*

int $ount = 3;

ouble aount = 33?;

'steoutprintf(*$ount is D an aount is Df*, $ount, aount);

ispla' $ount is 3 an aount is 33?""""

items

C i N d S i


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$$Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

Creating Normatted Strings

System/out/print4ormat, item1, item2, ///, itemk5

String/ormat4ormat, item1, item2, ///, itemk5

String s ? String/ormat4Acount is d and amount is A, $, $/$"55E

O P d


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$"Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

Operator Precedence

o) to evaluate 3 B = $ 4 B 35 1

O t P d


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Operator Precedence 8ar, 8ar//

, / (nar' plus an inus), 8ar,//8ar (t'pe) astin+

! (7ot)

0,E,D (Jultipli$ation, i8ision, an reainer)

,/ (inar' aition an subtra$tion)

= (oparison)

==,!=; (.Kualit')

& (n$onitional :7@)

^ (.x$lusi8e LM)

| (n$onitional LM)

&& (onitional :7@) hort/$ir$uit :7@

|| (onitional LM) hort/$ir$uit LM

=,=,/=,0=,E=,D= (:ssi+nent operator)

O t P d d # i ti it


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Operator Precedence and #ssociativity

The e+pression in the parentheses is evaluated irst/

4Parentheses can e nested, in )hich case the e+pressionin the inner parentheses is e+ecuted irst/5 (henevaluating an e+pression )ithout parentheses, theoperators are applied according to the precedence rule and

the associativity rule/

I operators )ith the same precedence are ne+t to eachother, their associativity determines the order o

evaluation/ #ll inary operators e+cept assignmentoperators are let0associative/

O t # i ti it


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$.Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

Operator #ssociativity

(hen t)o operators )ith the same precedenceare evaluated, the associativity o the operatorsdetermines the order o evaluation/ #ll inaryoperators e+cept assignment operators are left-

associative/ a B c d is e;uivalent to 44a 5 B c5 d

#ssignment operators are right-associative/

Thereore, the e+pression a ? B? c ? $ is e;uivalent to a ? 4 B? 4c ? $55

* l


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">Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

*+ample

#pplying the operator precedence and associativity rule,

the e+pression 3 B = $ 4 B 35 0 1 is evaluated asollo)s:

0 > 3 0 ( ) / 1

0 > 3 0 N 1

1? > 3 0 N 1

1? > 3 N 1

14 > 3 N 1

14 >

false

1 inside arentheses irst

425 multiplication

435 multiplication

45 addition

4$5 sutraction

4"5 greater than

O d * l ti O d


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"1Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. A rights reserved. 0!"#!222"$%!&

Operand *valuation Order

The precedence and associativity rulesspeciy the order o the operators, ut do not

speciy the order in )hich the operands o a

inary operator are evaluated/ Operands are

evaluated rom let to right in Java/

The left-hand operand of a binary operator is

evaluated before any part of the right-hand

operand is evaluated.

O d * l ti O d t


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Operand *valuation Order, cont/

I no operands haveside effectsthat change the valueo a variale, the order o operand evaluation isirrelevant/ Interesting cases arise )hen operands dohave a side eect/ Nor e+ample,xecomes 1 in theollo)ing code, ecause a is evaluated to > eore ++ais evaluated to 1/

int a ? >E

int + ? a B 4BBa5E

&utxecomes 2 in the ollo)ing code, ecause ++ais evaluated to 1, then ais evaluated to 1/

int a ? >E

int + ? BBa B aE

l * l ti * i


63/64


ule o *valuating an *+pression

ule 1: *valuate )hatever sue+pressions you can

possily evaluate rom let to right/

ule 2: The operators are applied according to their

precedence/

ule 3: The associativity rule applies or t)o operators

ne+t to each other )ith the same precedence/

l * l ti * i


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ule o *valuating an *+pression

#pplying the rule, the e+pression 3 B = $ 4 B 35 0 1is evaluated as ollo)s:

! 0 > 3 0 ( ! ) / 1

! 1? > 3 0 ( ! ) / 1

14 > 3 0 ( ! ) / 1

14 > 3 0 / 1

14 > 3 N 1

14 >

false

415 I is the irst sue+pression that can

e evaluated rom let/

425 3 B 1" is evaluated no)/

435 B 3 is no) the letmost sue+pression

that should e evaluated/

45 $ I 8 is evaluated no)/

4$5 3$ P 1 is evaluated no)/

4"5 1. = 3 is evaluated no)/

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