Java Reference
In-Depth Information
logical
expression
true
statement
false
FIGURE 5-1
while
loop
The
logical expression
provides an entry condition. If it initially evaluates to
true
,
the
statement
executes. The loop condition—the
logical expression
—is then
reevaluated. If it again evaluates to
true
, the
statement
executes again. The
statement
(body of the loop) continues to execute until the
logical expression
is
no longer
true
. A loop that continues to execute endlessly is called an infinite loop.
To avoid an infinite loop, make sure that the loop's body contains one or more
statements that ensure that the loop condition—the
logical expression
in the
while
statement—will eventually be
false
.
EXAMPLE 5-1
Consider the following Java program segment:
int
i = 0;
//Line 1
while
(i <= 20)
//Line 2
{
System.out.print(i + " ");
//Line 3
i = i + 5;
//Line 4
}
System.out.println();
//Line 5
Sample Run:
0 5 10 15 20
In Line 1, the variable
i
is set to
0
. The logical expression in the
while
statement (in Line 2),
i <= 20
, is then evaluated. Because the expression
i <= 20
evaluates to
true
, the body of
the
while
loop executes next. The body of the
while
loop consists of the statements in
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