On Windows (I used the MinGW version 3.3.1 of gcj), there's a bug if a
synchronized method calls wait(). If the method containing wait() was invoked by
another synchronized method of the same object, then the calling thread keeps
the lock on this object.

Example program:

If you run this with the Java 1.4.1 VM on Windows, the output is

a
c
c
c
...


If compiled with GCJ on Windows, the output is only

a


Code of the example program:

public class Test
{
  public static void main(String args[])
  {
    Test test = new Test();

    new MyThread(test).start();

    while(true)
    {
      try
      {
        Thread.sleep(1000);
      }
      catch (Exception e)
      {
        e.printStackTrace();
      }

      test.c();
    }
  }

  public synchronized void a()
  {
    System.out.println("a");

    b();
  }

  public synchronized void b()
  {
    try
    {
      wait();
    }
    catch (Exception e)
    {
      e.printStackTrace();
    }

    System.out.println("b");
  }

  public synchronized void c()
  {
    System.out.println("c");
  }
}


class MyThread extends Thread
{
  private Test test;

  public MyThread(Test test)
  {
    this.test = test;
  }

  public void run()
  {
    test.a();
  }
}