SELECTIONS - Introduction to Java Programming: Comprehensive Version - page 79

If the boolean-expression evaluates to true , the statements in the block are executed.
As an example, see the following code:

if (radius >= 0 ) {
area = radius * radius * PI;
System.out.println( "The area for the circle of radius " +
radius + " is " + area);
}

The flowchart of the preceding statement is shown in Figure 3.1b. If the value of radius
is greater than or equal to 0 , then the area is computed and the result is displayed; otherwise,
the two statements in the block will not be executed.
The boolean-expression is enclosed in parentheses. For example, the code in (a) is
wrong. It should be corrected, as shown in (b).

if i > 0 {
System.out.println( "i is positive" );
}

if (i > 0 ) {
System.out.println( "i is positive" );
}

(a) Wrong

(b) Correct

The block braces can be omitted if they enclose a single statement. For example, the fol-
lowing statements are equivalent.

if (i > 0 ){
System.out.println( "i is positive" );
}

if (i > 0 )
System.out.println( "i is positive" );

Equivalent

(a)

(b)

Note
Omitting braces makes the code shorter, but it is prone to errors. It is a common mistake
to forget the braces when you go back to modify the code that omits the braces.

Omitting braces or not

Listing 3.2 gives a program that prompts the user to enter an integer. If the number is a
multiple of 5 , the program displays HiFive . If the number is divisible by 2 , it displays HiEven .

L ISTING 3.2

SimpleIfDemo.java
1 import java.util.Scanner;
2
3 public class SimpleIfDemo {
4 public static void main(String[] args) {
5 Scanner input = new Scanner(System.in);
6 System.out.println( "Enter an integer: " );
7 int number = input.nextInt();

enter input

8
9 if (number % 5 == 0 )
10 System.out.println( "HiFive" );
11
12 if (number % 2 == 0 )
13 System.out.println( "HiEven" );
14 }
15 }

check 5

check even