Directing Program Flow - JAVA Programming for Engineers - page 80

the if and the switch constructs. The conditional operator (?:), which is
the only Java operator that contains three operands, is also used in deci-
sion-making constructs.

The if construct
The Java if construct consists of three elements:
1. The if keyword
2. A test expression, called a conditional clause
3. One or more statements that execute if the test expression is true
The following program, named BeepIf, displays the message
“BEEP-BEEP” if the user enters the number 1 or 2. Otherwise no message
is displayed. The code uses an if construct to test if the typed keystroke
matches the required numbers.

// File name: BeepIf.java

// Reference: Chapter 9

//
// Java program to demonstrate simple decision

// Topics:

// 1. Using the if construct

//
// Requires:

// 1. Keyin class in the current directory

public class BeepIf
{

public static void main(String[] args)
{

int userInput;

userInput = Keyin.inInt("Enter 1 or 2 to beep: ");
if(userInput == 1 || userInput == 2)
System.out.println("BEEP-BEEP");

}

}

The BeepIf program uses a simple form of the Java if construct. The
compiler evaluates the expression in parentheses, following the if key-
word, which in this case is

if(userInput == 1 || userInput == 2)

The expression uses the logical OR operator (discussed in Chapter 8)
to create a compound condition. The parenthetical expression evaluates
to true if the variable userInput is equal to 1 or 2. If the expression evalu-
ates to true, then the statement that follows is executed. If the expression