LOOPS - Introduction to Java Programming - page 135

count = 0;

loop-
continuation-
condition?

false false

(count < 100)?

true true

System.out.println("Welcome to Java!");
count++;

Statement(s)
(loop body)

(a) (b)

F IGURE 4.1 The while loop repeatedly executes the statements in the loop body when the
loop-continuation-condition evaluates to true .

loop-continuation-condition is count < 100 and the loop body contains the fol-
lowing two statements:

loop-continuation-condition

int count = 0 ;

while ( count < 100 ) {
System.out.println( "Welcome to Java!" ); loop body

count++;

}

In this example, you know exactly how many times the loop body needs to be executed
because the control variable count is used to count the number of executions. This type of
loop is known as a counter-controlled loop.

counter-controlled loop

Note
The loop-continuation-condition must always appear inside the parentheses.
The braces enclosing the loop body can be omitted only if the loop body contains one
or no statement.

Here is another example to help understand how a loop works.

int sum = 0 , i = 1 ;
while (i < 10 ) {
sum = sum + i;
i++;

}
System.out.println( "sum is " + sum); // sum is 45

If i < 10 is true , the program adds i to sum . Variable i is initially set to 1 , then is incre-
mented to 2 , 3 , and up to 10 . When i is 10 , i < 10 is false , so the loop exits. Therefore,
the sum is 1 + 2 + 3 + ... + 9 = 45 .
What happens if the loop is mistakenly written as follows?

int sum = 0 , i = 1 ;
while (i < 10 ) {
sum = sum + i;

}