/**
 * Causes this thread to begin execution; the Java Virtual Machine
 * calls the <code>run</code> method of this thread.
 */
public synchronized void start() {
        
        if (threadStatus != 0)
            throw new IllegalThreadStateException();
        
        group.add(this);

        boolean started = false;
        try {
            start0();//核心部分就是这个start0本地方法，也就是JNI方法，run方法就是被此方法调用
            started = true;
        } finally {
            try {
                if (!started) {
                    group.threadStartFailed(this);
                }
            } catch (Throwable ignore) {
                
            }
        }
    }