public void printRange( int num )
{
int count = 0 ;
while ( count < num )
{
System.out.println( count ) ;
count++
}
}
Suppose num is -1. Then, when we evaluate count < num,
we get 0 < -1. This evaluates to false.
When you write code for a while loop, always think about what kind of values may cause the loop body not to execute, and decide whether it behaves correctly when it doesn't run.