Changing the reference of the object?

Question

public class A {
  public static void change(X a, X b) {
    a = b;
    System.out.println("a:" + a + " b:" + b);
  public static void main(String[] args) {
    X a = new X(1);
    X b = new X(2);
    change(a,b);
    System.out.println("a:" + a + " b:" + b);
public class X {
  int k = 1;
  public X(int kk){
    k = kk;
  public String toString(){
    return k + "";
}Why is the output
a:2 b:2
a:1 b:2
not
a:2 b:2
a:2 b:2
Edited by: yeeen on Oct 5, 2009 12:22 PM

Answer 1

Here's another example:
public static void main(String[] args) {
    String[] s = {"foo", "bar"};
    changeReference(s);
    System.out.println(Arrays.toString(s)); // Still prints foo, bar. Reference is not changed.
    changeValue(s);
    System.out.println(Arrays.toString(s)); // Prints foo, foo. Value is changed.
public static void changeReference(String[] s) {
    s = new String[] {"bar", "bar"};
public static void changeValue(String[] s) {
    s[1] = "foo";
}