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Transcript of © 2007 Lawrenceville Press Slide 1 Chapter 5 The if Statement Conditional control structure, also...
© 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