Urgent: ThreadPool Issues

[luco zhao]

Hi, there,
I've got "java.lang.IllegalStateException: Unable to access thread pool due to java.lang.NullPointerException" error info when use org.apache.avalon.excalibur.thread.impl package to manage thread pool.

  public static void main(String[] args) {
        try {
            DefaultThreadPool dtp = new DefaultThreadPool("ThreadPoolTest", 1000);
            Thread t = null;
            while (true) {
                try {
//                    t = new Thread(new MyRunner());
//                    t.start();
                    ThreadControl tc = dtp.execute(new MyRunner());
                    Thread.sleep(1);
                }
                catch (InterruptedException ex) {
                }
            }

How to use the package, I got no idea about the exception described above. Thanks in advance!