Thread中的run()

    　　/* What will be run. */
    　　private Runnable target;
       如果线程在创建时传入了Runnable运行对象，那么该对象的run方法将被调用
 1     /**
 2      * If this thread was constructed using a separate
 3      * <code>Runnable</code> run object, then that
 4      * <code>Runnable</code> object‘s <code>run</code> method is called;
       否则，不做任何事且返回
 5      * otherwise, this method does nothing and returns.
 6      * <p>
　　　　Thread的子类应该重写这个方法 
 7      * Subclasses of <code>Thread</code> should override this method.
 8      *
 9      * @see     #start()
10      * @see     #stop()
11      * @see     #Thread(ThreadGroup, Runnable, String)
12      */
13     @Override
14     public void run() {
15         if (target != null) {
16             target.run();
17         }
18     }