week4 5 selection

8/12/2019 Week4 5 Selection

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2003 Prentice Hall, Inc. All rights reserved.

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Outline4.1 Introduction

4.2 Algorithms4.3 Pseudocode4.4 Control Structures4.5 if Single-Selection Statement4.6 if else Selection Statement4.7 Block Statement4.8 switch Multiple-Selection Statement4.9 Conditional And Operator4.10 Compound Assignment Operators

4.11 Increment and Decrement Operators4.12 Primitive Types

Chapter 4 - Control Structures: Part 1


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4.1 Introduction

We learn about Control Structures

Structured-programming principle

Control structures help build and manipulate objects(Chapter 8)


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4.2 Algorithms

Algorithm

Series of actions in specific order

The actions executed The order in which actions execute

Program control

Specifying the order in which actions execute Control structures help specify this order


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4.3 Pseudocode

Pseudocode

Informal language for developing algorithms

Not executed on computers

Helps developers think out algorithms


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4.4 Control Structures

Sequential execution

Program statements execute one after the other

Transfer of control Three control statements can specify order of statements

Sequence structure

Selection structure Repetition structure

Activity diagram

Models the workflow Action-state symbols

Transition arrows


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Fig 4.1 Sequence structure activity diagram.

add grade to total

add 1 to counter

Corresponding Java statement:total = total + grade;

Corresponding Java statement:counter = counter + 1;


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Java Keywords

abstract assert boolean break bytecase catch char class continuedefault do double else extendsfinal finally float for ifimplementsimport instanceofint interfacelong native new package privateprotected public return short staticstrictfp super switch synchronizedthisthrow throws transient try voidvolatile whileKeywords that are reserved, but not currently used

const gotoFig. 4.2 Java keywords.


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4.4 Control Structures

Java has a sequence structure built-in

Java provides three selection structures if

Ifelse

switch

Java provides three repetition structures while dowhile

do

Each of these words is a Java keyword


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4.5 if Single-Selection Statement

Single-entry/single-exit control structure

Perform action only when condition is true

Action/decision programming model


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Fig 4.3 if single-selections statement activity diagram.

[grade >= 60]

[grade < 60]

print Passed


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Example:

If student's grade is greater than or equal to 60

Print "Passed"

The preceding pseudocode If statement may be

written in Java as:

if ( studentGrade >= 60 )

System.out.println( "Passed" );


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4.6 ifelse Selection Statement

Perform action only when condition is true

Perform different specified action when condition

is false

For example, the pseudocode statement

If student's grade is greater than or equal to 60

Print "Passed"

Else

Print "Failed"


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Fig 4.4 ifelse double-selections statement activity diagram.

[grade >= 60][grade < 60]print Failed print Passed


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The preceding If...Else pseudocode statement can

be written in Java asif ( grade >= 60 )


Else

System.out.println( "Failed" );


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Conditional operator (?:)

Can be used in place of an if...else statement

For example, the statement

System.out.println( studentGrade >= 60 ? "Passed"

: "Failed" );


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4.6 Nested if...else Statements

A program can test multiple cases by placing

if...else statements inside other if...else statements

to create nested if...else statements.

For example, the following pseudocode represents

a nested if...else that :

prints A for exam grades greater than or equal to 81

B for grades in the range 70 to 79

C for grades in the range 60 to 69

D for grades in the range 50 to 59 E for all other grades


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Pseudocode:If student's grade is greater than or equal to 81

Print "A"else

If student's grade is greater than or equal to 70Print "B"

else

If student's grade is greater than or equal to 60Print "C"else

If student's grade is greater than or equal to 50Print "D"

elsePrint E"


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Most Java programmers prefer to write the precedingif...else statement as

if ( studentGrade >= 81 )System.out.println( "A" );

else if ( studentGrade >= 70 )

System.out.println( "B" );


System.out.println( "C" );


System.out.println( "D" );else

System.out.println( E" );


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if ( x > 5 )

if ( y > 5 )

System.out.println( "x and y are > 5" );

else

System.out.println( "x is 5" );}

else

System.out.println( "x is


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4.7 Block Statement

To include several statements in the body of an if

(or the body of an else for an if...else statement),

enclose the statements in braces ({ and }).

A set of statements contained within a pair of

braces is called a block.

A block can be placed anywhere in a program that

a single statement can be placed.


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4.7 Block Statement

The following example includes a block in the else-

part of an if...else statement:

if ( grade >= 60 )


else

{

System.out.println( "Failed" );

System.out.println( "You must take this course again." );

}


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4.8 switch Multiple-Selection Statement

switch statement

Used for multiple selections

Perform different actions based on the possible values of an

integer variable or expression

Each action. is associated with the value of a constant

integral expression (i.e., a constant value of type byte,

short, int or char, but not long) that the variable or

expression on which the switch is based may assume


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Fig. 4.5 switch multiple-selection statement activity diagram with break statements.

case a action(s) break

default action(s)

[true]

case b action(s) break

case z action(s) break

.

.

.

[false]

case a

[true]

[true]

case b

case z

[false]

[false]


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4.8 switch Multiple-Selection Statement

switch ( nilai/10){

case 10:case 9:

case 8: huruf='A';break;

case 7:huruf='B';break;

case 6:huruf='C';break;

case 5:huruf='D';

break;default:huruf='E';break;

}


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4.9 Conditional And Operator

if ( studentGrade >= 81 && studentGrade = 70 && studentGrade < 81 )

System.out.println( "B" );

else if ( studentGrade >= 60 && studentGrade < 70)

System.out.println( "C" );else if ( studentGrade >= 50 && studentGrade < 60 )

System.out.println( "D" );

elseSystem.out.println( E" );

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4.10 Compound Assignment Operators

Assignment Operators

Abbreviate assignment expressions

Any statement of form variable = variable operator expression;

Can be written as

variable operator= expression;

e.g., addition assignment operator +=

c = c + 3

can be written as

c += 3

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Assignmentoperator

Sampleexpression

Explanation Assigns

Assume:intc = 3,d = 5, e = 4, f

= 6, g = 12;+= c += 7 c = c + 7 10to c-= d -= 4 d = d - 4 1to d*= e *= 5 e = e * 5 20to e/= f /= 3 f = f / 3 2to f%=

g %= 9

g = g % 9

3to g

Fig. 4.12 Arithmet ic assignment operators.

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4.11 Increment and Decrement Operators

Unary increment operator (++) Increment variables value by 1

Unary decrement operator (--) Decrement variables value by 1

Preincrement / predecrement operator

Post-increment / post-decrement operator

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Operator Ca lled Sampleexpression

Explanation

++ preincrement ++a Increment aby 1, then use the newvalue of ain the expression inwhich aresides.

++ postincrement a++ Use the current value of ain theexpression in which aresides, thenincrement aby 1.

-- predecrement --b Decrement bby 1, then use the

new value of bin the expression inwhich bresides.-- postdecrement b-- Use the current value of bin the

expression in which bresides, thendecrement bby 1.

Fig. 4.13 The inc rement a nd dec rement opera tors.


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Operators Assoc iativity Type++ -- right to left unary postfix

++ -- + - (type) right to left unary* / % left to right multiplicative+ - left to right additive< >= left to right relational== != left to right equality?: right to left conditional= += -= *= /= %= right to left assignment

Fig. 4.15 Prec ed enc e a nd assoc ia tivity of the opera tors d isc ussed so fa r.

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4.12 Primitive Types

Primitive types

building blocks for more complicated types

Java is strongly typed All variables in a Java program must have a type

Java primitive types

portable across computer platforms that support Java

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Typ e Size in b its Va lues Sta nd ardboolean trueor false

[Note:The representation of a boolean is

specific to the Java Virtual Machine on each

computer platform.]char 16 '\u0000'to '\uFFFF'

(0 to 65535)

(ISO Unicode character set)

byte 8 128 to +127(2

7to 2

7 1)

short 16 32,768 to +32,767(2

15to 2

15 1)

int 32 2,147,483,648 to +2,147,483,647(2

31to 2

31 1)

long 64 9,223,372,036,854,775,808 to

+9,223,372,036,854,775,807(2

63to 2

63 1)

float 32 Negative range:3.4028234663852886E+38 to

1.40129846432481707e45

Positive range:

1.40129846432481707e45 to

3.4028234663852886E+38

(IEEE 754 floating point)

double 64 Negative range:1.7976931348623157E+308 to

4.94065645841246544e324

Positive range:

4.94065645841246544e324 to

1.7976931348623157E+308

(IEEE 754 floating point)

Fig. 4.16The Java primitive typ es.

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