Need some help understanding the last portion of this simple loop.

Question

public static void main(String[] args)
        int j = 3;
        for(int i = 5; i > j; i -= 3)
            do
                    System.out.printf("%-+3d, %-+3d\n", j, i);
            while(j-- >= 3);
    }Here is what I understand:
the for loop starts, with int i equal to 5 and j equal to 3. Since i > j, it runs the statement (Do While loop). The Do While loop prints the values to the screen. Then since j is equal to 3, it will do the Do While loop again, first decrementing j by 1. So j is 2 and i is 5.. those get printed. Then since j is not >= to 3, the loop ends and backs out to the For loop.
Here is where I am confused. I know that j gets decremented to 1 before it backs to the For loop. I understand everything so far. However, I know that the Do While loop runs again, printing 1 for j and 2 for i. So I gather that since i was greater than j, 3 was subtracted from i... then the Do While ran, printing the new values... and stopped because j isn't >=3. So j becomes zero (though it won't ever print that) but I don't understand how the loop finally ends.
Any hints? I tried looking at code examples in several books but none have that kind of thing.. only ones that talk about when i is less than a value to stop when that boolean is false. However in this code, i so far has always been greater than j.
What makes the loop end?
Thanks in advance,
SYD
Edited by: SYD527 on May 15, 2008 1:29 AM

Answer 1

Well this has to do with the fact that a do while loop checks its condition after running the content of the loop, so even
do  {
/* some code */
} while (false); will atleast run once.
Each time the for loop goes into a new iteration the do while loop is excecuted atleast once.
HTH
Lima