Programming and Problem Solving with Java

(^168) | Selection and Encapsulation
Statement1A
Statement 2
Statement1B
false true
if( Expression )
else
Figure 4.3 if-elseFlow of Control

The if-else Form

In Java, the ifstatement comes in two forms: the if-elseform and the ifform. Let’s look first

at if-else. Here is its syntax template:

The expression in parentheses must produce a booleanresult. At run time, the computer

evaluates the expression. If the value is true, the computer executes Statement1A. If the

value of the expression is false, it executes Statement1B. Statement1A is often called the then

clause; Statement1B is the else clause. Figure 4.3 illustrates the flow of control of the if-elsestate-

ment. In the figure, Statement2 is the next statement in the code after the entire ifstatement.

Notice that a Java ifstatement uses the reserved words ifand elsebut the thenclause

does not include the word then. The following code fragment shows how to write an ifstate-

ment. Observe the indentation of the thenclause and the elseclause, which makes the state-

ment easier to read. Also notice the placement of the statement following the ifstatement.

If-Statement (the if-else form)

if ( Expression )

Statement1A

Statement1B

else