The Type boolean

Boolean Expressions and Boolean Variables

The type boolean is a primitive type Variables of type boolean and Boolean expressions

can have only values of either true or false. Example:

if (number > 0)

System.out.println(“The number is positive.”);

else

System.out.println(“The number is negative or zero”);

Boolean Expressions and Boolean Variables (cont’d)

A Boolean variable can be given the value of a Boolean expression by using an assignment statement.

Example:

int number = -5;

boolean isPositive;

isPositive = (number > 0);

Boolean Expressions and Boolean Variables (cont’d)

A value can also be assigned in the declaration statement.

boolean isPositive = (number > 0); The previous example can be rewritten as follows:

if (isPositive)System.out.println(“The number

is positive.”);else

System.out.println(“The number is negative or zero”);

Naming Boolean Variables When naming a Boolean variable choose a

statement that will be true when the value of the Boolean expression is true.

Examples:boolean isPositive = (number > 0);

boolean systemsAreOK = (temperature <= 100) && (thrust >= 12000) && (cabinPressure > 30);

boolean lightsOn = true;

Precedence Rules

First: the unary operators +, -, ++, --, and ! Second: the binary arithmetic operators *, /, % Third: the binary arithmetic operators +, - Fourth: the boolean operators <, >, <=, >= Fifth: the boolean operators ==, != Sixth: the boolean operator & Seventh: the boolean operator ^ Eighth: the boolean operator | Ninth: the boolean operator && Tenth: the boolean operator ||

Truth Table for the && (and) Boolean Operator

Value of A Value of B Resulting Value of A && B

true true true

true false false

false true false

false false false

Truth Table for the || (or) Boolean Operator

Value of A Value of B Resulting Value of A || B

true true true

true false true

false true true

false false false

Truth Table for the ^ ( exclusive or) Boolean Operator

Value of A Value of B Resulting Value of A ^ B

true true false

true false true

false true true

false false false

Truth Table for the ! (not) Boolean Operator

Value of A Resulting Value of !A

true false

false true

Input and Output of Boolean Values

The values true and false of the type boolean can be input and output the same way that values of the other primitive types

Example:boolean booleanVar = false;System.out.println(booleanVar);System.out.println(“Enter a boolean

value:”);Scanner keyboard =

new.Scanner(System.in);booleanVar = keyboard.nextBoolean();System.out.println(“You entered “ +

booleanVar);