loop

[anushree ari]

hi ranchers,
i came through this question in dan's latest exam,
how the loop works, explanation that dan gave is not suffecient for me, anybody could reply my question?

class E {
  public static void main (String[] args) {
    int i = 0, j = 0;
    while (i++ < 3) do
      System.out.print(j);
    while (j++ < 3);
  }
}

[ Jess added UBB [code] tags to preserve whitespace -- check 'em out! ]
[ November 19, 2002: Message edited by: Jessica Sant ]

[Jessica Sant]

Does it help if you break things up with a lil bit of formatting and whitespace?

class E 
{
  public static void main (String[] args) 
  {
    int i = 0, j = 0;
    while (i++ < 3)
    {
        do
        {
            System.out.print(j);
        }
        while (j++ < 3);
    }
  }
}

step through it line by line as if you were the JVM.
*Remember that in a while statement -- you first run the test -- then execute the code in the middle.
With a do while you first execute the statement in the middle -- then run the test.*
outer loop test i++<3 TRUE (i=1)
prints j=0
inner loop test j++<3 TRUE (j=1)
prints j=1
inner loop test j++<3 TRUE (j=2)
prints j=2
inner loop test j++<3 TRUE (j=3)
prints j=3
inner loop test j++<3 FALSE(j=4)
outer loop test i++<3 TRUE (i=2)
prints j=4
inner loop test j++<3 FALSE(j=5)
outer loop test i++<3 TRUE (i=3)
prints j=5
inner loop test j++<3 FALSE(j=6)
outer loop test i++<3 FALSE(i=4)
END
.... its kinda like some country song I heard -- sometimes you're the windshield, sometimes you're the bug. With the SCPJ test -- sometimes you have to be the compiler, sometimes the JVM. (ok... bad anaolgy -- but at least I tried)
[ November 19, 2002: Message edited by: Jessica Sant ]

[anushree ari]

thx jess,
this helps very well,
thankyou,

[Dan Chisholm]

A quick way to check a question like this is by adding more information to the print statement as follows.

class E {
  public static void main (String[] args) {
    int i = 0, j = 0;
    while (i++ < 3) {
      do {
        System.out.print("("+i+","+j+")");
      } while (j++ < 3);
    }
  }
}

The result is: (1,0)(1,1)(1,2)(1,3)(2,4)(3,5).