array object reference in a method

[sindura kapur]

according to me the output of following code

public class Test {
    int a;
    int[] b;
    public void f() {
        a = 0;
        b = new int[]{1,2};
        change(b, a);
        System.out.println(a + " " + b[0] + " ");
    }
    public void change(int[] x, int y) {
        y = 10;
        x[0] = 10;
    }
    public static void main(String[] args) {
        Test obj = new Test();
        obj.f();
    } 

should be 10 10 BUT ACTUALLY IT IS 0 10.can anyone explain me how and why is that output changes b but not a?


[HENRY: Added code tags]
[ July 26, 2008: Message edited by: Henry Wong ]

[Henry Wong]

http://faq.javaranch.com/java/CallByReferenceVsCallByValue

[BV Boose]

when you pass a parameter in java it's by value, for primitives you're passing a copy of the primitive. For objects you're passing a copy of the REFERENCE to the object. Changing the copy of a doesn't change a, but the copy of the reference to b still points to the actual b object. For a more consistent example make change:

 public void change(int[] x, int y) {
        y = 10;
        x = null;
    }   

Originally posted by sindura kapur:
according to me the output of following code

public class Test {
    int a;
    int[] b;
    public void f() {
        a = 0;
        b = new int[]{1,2};
        change(b, a);
        System.out.println(a + " " + b[0] + " ");
    }
    public void change(int[] x, int y) {
        y = 10;
        x[0] = 10;
    }
    public static void main(String[] args) {
        Test obj = new Test();
        obj.f();
    } 

should be 10 10 BUT ACTUALLY IT IS 0 10.can anyone explain me how and why is that output changes b but not a?


[HENRY: Added code tags]

[ July 26, 2008: Message edited by: Henry Wong ]

[ July 27, 2008: Message edited by: gebuh Boose ]

[Garrett OBrien]

Originally posted by Henry Wong:
http://faq.javaranch.com/java/CallByReferenceVsCallByValue

When I first saw this link, I got very nervous, till I read it. This whole thing of "pass by reference" vs "pass by value" is annoying because people don't understand what the terms mean. As the link states, Java is only pass by value, there is no pass by reference, although, you can simulate it by putting your variables in a class.

Garrett