Synchronizing unrelated threads - java.lang.IllegalMonitorStateException

Question

Hi,
I'm trying to synchronize two unrelated threads using a third object, but getting java.lang.IllegalMonitorStateException: current thread not owner error. Does any one know what am I doing wrong and how to fix it. A simulated code is posted below.
Thanks in advance.
// ----------- beginning of code --------------------------
// Code that throws java.lang.IllegalMonitorStateException: current thread not owner error.
public class ThreadTest
public static void log( String message )
     System.out.println( Thread.currentThread().getName() + ":" + message );
public static void main( String args[] )
     Thread thread1 = new Thread1();
     Thread thread2 = new Thread2();
     thread1.start();
     thread2.start();
     try
     thread1.join();
     thread2.join();
     catch (InterruptedException e)
     e.printStackTrace();
     log( "All Done...");
class Thread1 extends Thread
public void run()
     synchronized( Common.done )
     while (!Common.done.booleanValue())
          ThreadTest.log("Waiting on Common.done");
          try
          Common.done.wait();
          catch (InterruptedException e)
          e.printStackTrace();
class Thread2 extends Thread
public void run()
     synchronized( Common.done )
     ThreadTest.log( "Sleeping for 10 seconds ");
     try
          Thread.sleep( 10 * 1000 );
     catch (InterruptedException e)
          e.printStackTrace();
     ThreadTest.log( "Calling notifyAll");
     Common.done = Boolean.TRUE;
     // ******* Why am I getting 'java.lang.IllegalMonitorStateException: current thread not owner' in the next line
     Common.done.notifyAll();
class Common
public static Boolean done = Boolean.FALSE;
// ----------- end of code --------------------------

Answer 1

// ******* Why am I getting'java.lang.IllegalMonitorStateException:
current thread not owner' in the next line
Common.done.notifyAll(); Because x.notifyAll() has to be inside a
synchronized(x) block.
The code you posted looks like it meets that
criteria, so I would have to conclude the code you
posted does not represent the actual code you are
running.Hi.. It is inside synchronized( Common.done) block... Thats why I'm confused....