// SleepTest.java的源码
 class ThreadA extends Thread{
   public ThreadA(String name){ 
     super(name); 
   } 
   public synchronized void run() { 
     try {
       for(int i=0; i <10; i++){ 
         System.out.printf("%s: %d\n", this.getName(), i); 
        // i能被4整除时，休眠100毫秒
         if (i%4 == 0)
           Thread.sleep();
       } 
     } catch (InterruptedException e) {
       e.printStackTrace();
     }
   } 
 } 
 public class SleepTest{ 
   public static void main(String[] args){ 
     ThreadA t1 = new ThreadA("t1"); 
     t.start(); 
   } 
 } 

 // SleepLockTest.java的源码
 public class SleepLockTest{ 
   private static Object obj = new Object();
   public static void main(String[] args){ 
    ThreadA t1 = new ThreadA("t1"); 
     ThreadA t2 = new ThreadA("t2"); 
     t1.start(); 
    t2.start();
   } 
   static class ThreadA extends Thread{
     public ThreadA(String name){ 
       super(name); 
     } 
     public void run(){ 
       // 获取obj对象的同步锁
       synchronized (obj) {
         try {
          for(int i=0; i <10; i++){ 
             System.out.printf("%s: %d\n", this.getName(), i); 
            // i能被4整除时，休眠100毫秒
             if (i%4 == 0)
              Thread.sleep(100);
           }
         } catch (InterruptedException e) {
           e.printStackTrace();
         }
       }
     } 
   } 
 } 

// SleepLockTest.java的源码(注释掉synchronized(obj))
 public class SleepLockTest{ 
   private static Object obj = new Object();
   public static void main(String[] args){ 
    ThreadA t1 = new ThreadA("t1"); 
    ThreadA t2 = new ThreadA("t2"); 
     t.start(); 
     t.start();
   } 
   static class ThreadA extends Thread{
     public ThreadA(String name){ 
       super(name); 
     } 
     public void run(){ 
       // 获取obj对象的同步锁
 //      synchronized (obj) {
         try {
          for(int i=0; i <10; i++){ 
             System.out.printf("%s: %d\n", this.getName(), i); 
            // i能被4整除时，休眠100毫秒
            if (i%4 == 0)
               Thread.sleep(100);
           }
         } catch (InterruptedException e) {
           e.printStackTrace();
         }
 //      }
     } 
   } 
 }