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© 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.

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© 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

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© 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.

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© 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.

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© 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.

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© 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; }

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© 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

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© 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.

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© 2007 Lawrenceville Press Slide 9 Chapter 5 And Truth Table And Exp1Exp2Result True False TrueFalse

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

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

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© 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

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© 2007 Lawrenceville Press Slide 13 Chapter 5 Flowchart Symbols decision

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© 2007 Lawrenceville Press Slide 14 Chapter 5 The RPS Flowchart

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