Bottom-driven Loop
All loops must do three things:
- The loop must be initialized correctly.
- The ending condition must be tested correcly.
- The body of the loop must change the condition that is tested.
The code fragment includes all three,
but in a different order than usual.
The ending condition test is done after the loop body has executed.
int count = 0; // initialize count to 0
do
{
System.out.println( count ); // loop body: includes code to
count++ ; // change the count
}
while ( count < 10 ); // test if the loop body should be
// executed again.
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Recall that loops with the test the top of the loop
(while and do loops)
are called top-driven loops.
Loops implemented with the test at the bottom
are sometimes called bottom-driven loops.
This location for the ending test has some odd (and sometimes undesirable) effects.
For example:
int count = 1000;
do
{
System.out.println( count );
count++ ;
}
while ( count < 10 );
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