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"John Fu" <zenki@ihug.com.au> wrote in message
news:8tgikk$gk6$1@bugstomper.ihug.com.au...

> I have a problem with my code. And I find that my swap method isn't really
> swapping the elements declared in my arrays. Can someone help please.  I
> know it's just something simple that I'm missing, but I just can't catch
it.
> Thanks.

> public class test
> {
>      static int[] pos = new int[3];
>      public static void main(String args[]) throws Exception
>      {
>           pos[0] = 1;
>           pos[1] = 2;
>           pos[2] = 3;
>           swap(pos[0],pos[1]);
>           System.out.println("pos[0] = "+pos[0]);
>           System.out.println("pos[1] = "+pos[1]);
>           System.out.println("pos[2] = "+pos[2]);
>      }//end main
>      public static void swap(int x, int y) throws Exception
>      {
>           int tmp;
>           tmp = x;
>           x = y;
>           y = tmp;
>      }//end swap
> }

Primitive values in Java are pass by value - so all you are doing is
swapping the
local variables x and y.

References (Objects) are done by passing the reference by value so what
you want to do will not work there either.

You could write a swap methods like:

public static void swap(int[] array, int src, int dst)
{
    int tmp;

    tmp = array[src];
    array[src] = array[dst];
    array[dst] = tmp;
}

src and dst are probably bad names... but you get the idea I hope.

Why are you declaring that it throws "Exception"?  It isn't needed
and it is generaly a bad idea to throw/catch "Exception" - you should
be dealing with the appropriate subclass.

..darcy