What's wrong with my code? why ins the end x is not 0 and y is not 400000 ?

Question

public class ThreadTest extends Thread {
     static int x = 0;
     static long y = 0;
     @Override
     public void run() {
          changeValues();
     private void changeValues() {
          for(int i=0; i<100000; i++) {
               increaseX();
               increaseY();
               decreaseX();               
     private synchronized void increaseX() {
          x += 1;
     private synchronized void increaseY() {
          y += 2;          
     private synchronized void decreaseX() {
          x -= 1;
     public synchronized int getX() {
          return x;
     public synchronized long getY() {
          return y;
     * @param args
     public static void main(String[] args) {
          ThreadTest t1 = new ThreadTest();
          ThreadTest t2 = new ThreadTest();
          t1.start();
          t2.start();
          try {
               t1.join();
               t2.join();               
          catch (Exception e) {
               System.out.println("Error occured");
          System.out.println("x="+t1.getX()+", y="+t1.getY());
          System.out.println("x="+t2.getX()+", y="+t2.getY());
}

Answer 1

...forgot about I was actually trying to synchronize different objects ....
Concurrency makes you feel confused and rookie :(:) {noformat}"...no one can write correct programs in a language where 'a=a+1' is not deterministic."{noformat} +// [The Evolution of Lua (Section 5.4)|http://www.tecgraf.puc-rio.br/~lhf/ftp/doc/hopl.pdf|source]+
class Unbelievable implements Runnable {
    private volatile int data;
    public void increase() {
        synchronized (new Object()) {
            int tmp = ++data;
            if(tmp != data) {System.out.println("unbelievable! " + tmp);}
    public void run() { while (true) { increase(); } }
    public static void main(String[] args) {
        final Unbelievable unbelievable = new Unbelievable();
        new Thread(unbelievable).start();
        new Thread(unbelievable).start();
}Edited by: gnat on Jan 15, 2010 1:00 PM