多线程顺序输出ABC

代码

package com.gallant.test;

/**
 * @author : 会灰翔的灰机
 * @date : 2021/2/14
 */
public class AbcTask {

  private static final int COUNT = 10;

  public static void main(String[] args) throws InterruptedException {
    Object a = new Object();
    Object b = new Object();
    Object c = new Object();
    new AbcThread(a, b, "A").start();
    new AbcThread(b, c, "B").start();
    Thread.sleep(1);
    new AbcThread(c, a, "C").start();
  }

  static class AbcThread extends Thread {
    private final Object parent;
    private final Object child;
    private final String value;

    public AbcThread(Object parent, Object child, String value) {
      this.parent = parent;
      this.child = child;
      this.value = value;
    }

    @Override
    public void run() {
      for (int i = 0; i < COUNT; i++) {
        synchronized (parent) {
          synchronized (child) {
            System.out.println(this.getName() + ":" + value);
            child.notifyAll();
          }
          try {
            parent.wait(1000);
          } catch (Exception e) {
            e.printStackTrace();
          }
        }
      }
    }
  }

}

输出

Thread-0:A
Thread-1:B
Thread-2:C
Thread-0:A
Thread-1:B
Thread-2:C
Thread-0:A
Thread-1:B
Thread-2:C
Thread-0:A
Thread-1:B
Thread-2:C
Thread-0:A
Thread-1:B
Thread-2:C
Thread-0:A
Thread-1:B
Thread-2:C
Thread-0:A
Thread-1:B
Thread-2:C
Thread-0:A
Thread-1:B
Thread-2:C
Thread-0:A
Thread-1:B
Thread-2:C
Thread-0:A
Thread-1:B
Thread-2:C

Process finished with exit code 0

总结

线程锁获取与释放过程
valueA线程：锁A->锁B->执行A->唤醒锁B->释放锁B->等待锁A唤醒并释放锁A
valueB线程：锁B->锁C->执行B->唤醒锁C->释放锁C->等待锁B唤醒并释放锁B
valueC线程：锁C->锁A->执行C->唤醒锁A->释放锁A->等待锁C唤醒并释放锁C