© 2007 Lawrenceville Press Slide 1 Chapter 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 statement if (x == 5) { y = 20; } assigns the value 20 to y only if x is equal to 5.

© 2007 Lawrenceville Press Slide 2 Chapter 5 Relational Operators OperatorMeaning == equal < less than <= less than or equal > greater than >= greater than or equal != not equal

© 2007 Lawrenceville Press Slide 3 Chapter 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 Press Slide 4 Chapter 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 Press Slide 5 Chapter 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 Press Slide 6 Chapter 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 Press Slide 7 Chapter 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 Press Slide 8 Chapter 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 Press Slide 9 Chapter 5 And Truth Table And Exp1Exp2Result True False TrueFalse

© 2007 Lawrenceville Press Slide 10 Chapter 5 Or Truth Table Or Exp1Exp2Result True FalseTrue FalseTrue False

© 2007 Lawrenceville Press Slide 11 Chapter 5 Not Truth Table Not ExpResult TrueFalse True

© 2007 Lawrenceville Press Slide 12 Chapter 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 Press Slide 13 Chapter 5 Flowchart Symbols decision

© 2007 Lawrenceville Press Slide 14 Chapter 5 The RPS Flowchart