© 2007 Lawrenceville PressSlide 1

Chapter 5

The if StatementChapter 5

The if Statement

Conditional control structure, also called a decision structure

Executes a set of statements when a condition is true

The condition is a Boolean expression

For example, the statementif (x == 5) {

y = 20;}

assigns the value 20 to y only if x is equal to 5.

© 2007 Lawrenceville PressSlide 2

Chapter 5

Relational OperatorsChapter 5

Relational Operators

Operator Meaning== equal< less than<= less than or equal> greater than>= greater than or equal!= not equal

© 2007 Lawrenceville PressSlide 3

Chapter 5

The if-else StatementChapter 5

The if-else Statement

Contains an else clause that is executed when the if condition evaluates to false. For example, the statement

if (x == 5) {y = 20;

} else {y = 10;

}assigns the value 20 to y if x is equal to 5 or the value 10 if x is not equal to 5.

© 2007 Lawrenceville PressSlide 4

Chapter 5

Nested if-else StatementsChapter 5

Nested if-else Statements

Should be indented to make the logic clear. Nested statement executed only when the

branch it is in is executed. For example, the statement

if (x == 5) {y = 20;

} else {if (x > 5) {

y = 10;} else {

y = 0;}

}evaluates the nested if-else only when x is not equal to 5.

© 2007 Lawrenceville PressSlide 5

Chapter 5

The if-else if StatementChapter 5

The if-else if Statement

Used to decide among three or more actions.

Conditions must be properly ordered for the statement to evaluate as expected. For example, the statement

if (x < 5) {y = 20;

} else if (x < 10) {y = 40;

} else if (x < 15) {y = 80;

} would give very different results if the conditions were ordered differently.

© 2007 Lawrenceville PressSlide 6

Chapter 5

The switch StatementChapter 5

The switch Statement

Used to decide among three or more actions.

Uses an expression that evaluates to an integer.

The break statement moves program execution to the next statement after the switch.

The default code is optional and is executed when none of the previous cases are met:switch (numLegs) {

case 2: System.out.println("human"); break;case 4: System.out.println("beast"); break;case 8: System.out.println("insect"); break;default: System.out.println("???"); break;

}

© 2007 Lawrenceville PressSlide 7

Chapter 5

The Math ClassChapter 5

The Math Class

Part of the java.lang package

The random() methods generates a double between 0 and 1.0. For example,

double rNum;rNum = Math.random();

A random integer in a range is generated by using the expression:(highNum – lowNum + 1) * Math.random() + lowNum

© 2007 Lawrenceville PressSlide 8

Chapter 5

Compound Boolean ExpressionsChapter 5

Compound Boolean Expressions

More than one Boolean expression in a single condition.

Formed using the logical And (&&), logical Or (||), or logical Not (!) operators.

© 2007 Lawrenceville PressSlide 9

Chapter 5

And Truth TableChapter 5

And Truth Table

And

Exp1 Exp2 Result

True True True

True False False

False True False

False False False

© 2007 Lawrenceville PressSlide 10

Chapter 5

Or Truth TableChapter 5

Or Truth Table

Or

Exp1 Exp2 Result

True True True

True False True

False True True

False False False

© 2007 Lawrenceville PressSlide 11

Chapter 5

Not Truth TableChapter 5

Not Truth Table

Not

Exp Result

True False

False True

© 2007 Lawrenceville PressSlide 12

Chapter 5

The Math ClassChapter 5

The Math Class

Part of the java.lang package

Methods include:

abs(num) returns the absolute value of num

pow(num1, num2) returns num1 raised to the num2 power

sqrt(num) returns the square root of num, where num is a positive number

© 2007 Lawrenceville PressSlide 13

Chapter 5

Flowchart SymbolsChapter 5

Flowchart Symbols

decision

© 2007 Lawrenceville PressSlide 14

Chapter 5

The RPS FlowchartChapter 5

The RPS Flowchart