使用Semaphore 信号量实现,获取用semphore.acquire()消费一个使用许可,release()创建一个消费许可
package com.atguigu.springboot;

import java.util.concurrent.Semaphore;

public class ThreeThread {
    private static Semaphore semaphoreA = new Semaphore(1);
    private static Semaphore semaphoreB = new Semaphore(0);
    private static Semaphore semaphoreC = new Semaphore(0);

    static class  printDemo{
        public void printA(){
            print('A', semaphoreA, semaphoreB);
        }

        public void printB(){
            print('B', semaphoreB, semaphoreC);
        }

        public void printC(){
            print('C',semaphoreC, semaphoreA);
        }

        private void print(char name, Semaphore semaphore, Semaphore nextSemphore)
        {
            for (int i = 0;i < 10; i++){
                try {
                    semaphore.acquire();
                    System.out.println(name + " i:" + i);
                    nextSemphore.release();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

            }
        }
    }

    public static void main(String[] args) {
        final printDemo printDemo = new printDemo();
        new Thread(){
            @Override
            public void run(){
                printDemo.printA();
            }
        }.start();

        new Thread(){
            @Override
            public void run(){
                printDemo.printB();
            }
        }.start();

        new Thread(){
            @Override
            public void run(){
                printDemo.printC();
            }
        }.start();
    }

}