java线程调用两次start()报错源码

 public synchronized void start()
    {
        if(threadStatus != 0 || this != me)
            throw new IllegalThreadStateException();
        group.add(this);
        start0();
        if(stopBeforeStart)
            stop0(throwableFromStop);
    }

    private native void start0();
 public synchronized void start()
    {