Java Reference
In-Depth Information
sum = 0;
isNegative =
false
;
while
(console.hasNext() && !isNegative)
{
num = console.nextInt();
if
(num < 0)
//if the number is negative, terminate the
//loop after this iteration
{
System.out.println("Negative number found in the data.");
isNegative =
true
;
}
else
sum = sum + num;
}
This
while
loop is supposed to find the sum of a set of positive numbers. If the data set
contains a negative number, the loop terminates with an appropriate error message. This
while
loop uses the flag variable
isNegative
to accomplish the desired result. The variable
isNegative
is initialized to
false
before the
while
loop. Before adding
num
to
sum
,the
code checks whether
num
is negative. If
num
is negative, an error message appears on
the screen and
isNegative
is set to
true
. In the next iteration, when the expression in
the
while
statementisevaluated,itevaluatesto
false
because
!isNegative
is
false
.
(Note that because
isNegative
is
true
,
!isNegative
is
false
.)
The following
while
loop is written without using the variable
isNegative
:
sum = 0;
while
(console.hasNext())
{
num = console.nextInt();
if
(num < 0)
//if the number is negative, terminate the loop
{
System.out.println("Negative number found in the data.");
break
;
}
sum = sum + num;
}
In this form of the
while
loop, when a negative number is found, the expression in the
if
statement evaluates to
true
; after printing an appropriate message, the
break
state-
ment terminates the loop. (After executing the
break
statement in a loop, the remaining
statements in the loop are skipped.)
The
continue
statement is used in
while
,
for
, and
do
...
while
structures. When the
continue
statement is executed in a loop, it skips the remaining statements in the loop
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