Synchronized thread monitors!!! AHHH!!!

Question

Hi,
In my program , I'm trying to start a thread which immediately begins waiting and when a notify is received the Thread executes a method and then right back to waiting. The program I'm having trouble writing is far too bulky and complicated to be easily made sense of here, so I've written this concise version:
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
import java.util.*;
class syncTest1 {
     public static void main(String[] args) {
          syncTest2 thread = new syncTest2();
          Monitor monitor = new Monitor();
          try {
               for(int i = 1; i <= 100; i++) {
                    synchronized(monitor) {
                         System.out.println("Notifying...");
                         monitor.notify();
                         Thread.sleep(500);
          } catch(InterruptedException ie) {}
class syncTest2 extends Thread {
     Monitor monitor;
     syncTest2() {}
     public void run() {
          try {
               while (monitor.progress() < 100) {
                    synchronized(monitor) {
                         monitor.wait();
                         monitor.increment(1);
                         System.out.println("Notified! Progress = " + monitor);
          } catch(InterruptedException ie) {}
     public Monitor getMonitor() { return monitor; }
// Used to store a dynamic integer value that can passed around as a synchronized monitor
class Monitor {
     int Int;
     Monitor() { Int = 0; }
     public void increment(int howMuch) { Int += Math.abs(howMuch); }
     public void decrement(int howMuch) { Int -= Math.abs(howMuch) * -1; }
     public  int progress() { return Int; }
}<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
When ran, this is the output:
java syncTest1
Notifying...
Notifying...
Notifying...
Notifying...
Notifying...
Notifying...
Notifying...
<and so on>
Notice how the monitor is never notified and syncTest1's monitor is still reacquired and able to be notified. I assume the problem lies somewhere in the trading of the monitor between classes, but for the life of me, I can't figure this one out...
Any help at all would be appreciated.
Thanks,
Jick

Answer 1

There are 2 things wrong.
1) You did not start your your thread.
2) You were not synchronizing on the same object.
I have also made some cosmetic changes but you are free to remove them.
import java.util.*;
public class Test20041229
    public static void main(String[] args)
        syncTest2 thread = new syncTest2();
        Monitor monitor = thread.getMonitor();//new Monitor(); !!!!!!!!!!!!!!!!!!!!!!!!!!
        thread.start(); // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1
        for(int i = 1; i <= 100; i++)
            synchronized(monitor)
                System.out.println("Notifying..." + i);
                monitor.notify();
                try
                    monitor.wait(500);
                } catch(InterruptedException ie)
class syncTest2 extends Thread
    Monitor monitor = new Monitor();
    syncTest2()
    public void run()
        while (monitor.progress() < 100)
            synchronized(monitor)
                try
                    monitor.wait();
                } catch(InterruptedException ie)
                monitor.increment(1);
                System.out.println("Notified! Progress = " + monitor);
    public Monitor getMonitor()
    { return monitor; }
// Used to store a dynamic integer value that can passed around as a synchronized monitor
class Monitor
    int Int;
    Monitor()
    { Int = 0; }
    public void increment(int howMuch)
    { Int += Math.abs(howMuch); }
    public void decrement(int howMuch)
    { Int -= Math.abs(howMuch) * -1; }
    public  int progress()
    { return Int; }
    public String toString()
        return "Monitor(" + Int + ")";
}