面试题多线程ABC顺序打印，不能使用sleep

package com.study.thread;   
  
/**  
 *  
 * @author nirvana  
 */  
public class MyThreadPrinter {   
  
    public static void main(String[] args) {   
  
        MyLock lock = new MyLock();   
  
        Thread a = new Thread(new MyPrinter("A", "B", lock));   
        Thread b = new Thread(new MyPrinter("B", "C", lock));   
        Thread c = new Thread(new MyPrinter("C", "A", lock));   
  
        a.start();   
        b.start();   
        c.start();   
  
        lock.setHolder("A");   
    }   
  
    static class MyPrinter implements Runnable {   
  
        private String myName;   
        private String nextName;   
        private final MyLock lock;   
  
        public MyPrinter(String myName, String nextName, MyLock lock) {   
            this.myName = myName;   
            this.nextName = nextName;   
            this.lock = lock;   
        }   
  
        public void run() {   
            int count = 10;   
            while (count > 0) {   
                //   
                if (lock != null && lock.getHolder() != null && lock.getHolder().equals(myName)) {   
                    synchronized (lock) {   
                        System.out.println(myName);   
                        count--;   
                        lock.setHolder(nextName);   
                    }   
                }   
  
            }   
        }   
    }   
  
    static class MyLock {   
  
        public MyLock() {   
        }   
        private String holder;   
  
        public String getHolder() {   
            return holder;   
        }   
  
        public void setHolder(String holder) {   
            this.holder = holder;   
        }   
    }   
}