Counting Upwards by Two's

If you change one of these three parts, the loop will do something different. Here is a section of a Java program that counts upwards by two's:

int count = 0;            // count is initialized
while ( count <= 6 )      // count is tested
{
  System.out.println( "count is:" + count );
  count = count + 2;      // count is increased by 2
}
System.out.println( "Done counting by two's." );      

Here is what the program prints:

count is: 0
count is: 2
count is: 4
count is: 6
Done counting by two's.

Here is what happens, step-by-tedious-step:

1. count is initialized to 0.
2. The condition, count <= 6 is evaluated, yielding TRUE.
3. The loop body is executed, printing "count is: 0" and adding 2 to count.
   • count is now 2.
4. The condition, count <= 6 is evaluated, yielding TRUE
.
5. The loop body is executed, printing "count is: 2" and adding 2 to count.
   • count is now 4.
6. The condition, count <= 6 is evaluated, yielding TRUE.
7. The loop body is executed, printing "count is: 4" and adding 2 to count.
   • count is now 6.
8. The condition, count <= 6 is evaluated, yielding TRUE.
9. The loop body is executed, printing "count is: 6" and adding 2 to count.
   • count is now 8.
10. The condition, count <= 6 is evaluated, yielding FALSE.
11. The body of the loop is skipped and the statement after the body is executed.