* @param Thread , Runnable

* >> 实现功能都一样，但Runnable是面向接口，扩展性比extends Thread 好；

* >> java是单继承，而接口可以实现多个；

*/
      public static class xc{
      public static long a=0;public static Object obj=new Object();public static void fun(){synchronized (obj) {DecimalFormat df=new DecimalFormat("000");System.out.println(Thread.currentThread().getName()+":"+df.format(a));a++;if(a>999){System.exit(0);}}}
                  }
                  public static class xc1 extends Thread{
            public void run() {while(true){try {Thread.sleep(10);} catch (Exception e) {e.printStackTrace();}xc.fun();}}}
                                    public static class xc2 implements Runnable{
                              public void run() {while(true){try {Thread.sleep(10);} catch (Exception e) {e.printStackTrace();}xc.fun();}}}
                                                      public static void main(String[] args) {
                                                      xc1 x1 = new xc1();xc2 x2 = new xc2();Thread t1=new Thread(x1);t1.setName("t1");Thread t2=new Thread(x2);t2.setName("t2");Thread t3=new Thread(x1);t3.setName("t3");Thread t4=new Thread(x2);t4.setName("t4");t1.start();t2.start();t3.start();t4.start();}
                                                }