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Do-while loop?

Abhi vijay
Ranch Hand

Joined: Sep 16, 2008
Posts: 509
Source: K&B Book.

1. public class Test {
2. public static void main(String [] args) {
3. int I = 1;
4. do while ( I < 1 )
5. System.out.print("I is " + I);
6. while ( I > 1 ) ;
7. }
8. }

The answer is no output is produce.
But isnt there a compilation error???
Rob Spoor
Sheriff

Joined: Oct 27, 2005
Posts: 19720
    
  20


I've added better indentation (which was left out on purpose in the book) so you can see the real flow.

The trick is, this is a while loop inside a do-while loop, which is perfectly fine.

Now as to why there is no output.
The inner loop itself is executed at least one. However, it's guard yields false immediately, so its body (the print) is not executed. Next the outer loop's guard is evaluated, and it too is false, thereby ending this loop too.


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Campbell Ritchie
Sheriff

Joined: Oct 13, 2005
Posts: 39415
    
  28
That's what I thought because there is no semicolon after the first while() but I tried it and it compiled and ran very boringly.

That is peculiar since the do-while there doesn't appear to fit into the form in the JLS.

Anybody else got any ideas?
Campbell Ritchie
Sheriff

Joined: Oct 13, 2005
Posts: 39415
    
  28
Yes, Rob is right.
Abhi vijay
Ranch Hand

Joined: Sep 16, 2008
Posts: 509
Thanks,Rob.
 
It is sorta covered in the JavaRanch Style Guide.
 
subject: Do-while loop?