java多線程，三個線程順序打印ABC，打印5次。使用三個Semaphore實現。

package com.zhong.thread;

import java.util.concurrent.Semaphore;

/**
 * 使用Semaphore實現三個線程順序打印ABC 5次
 */
public class MultipleThreadRotationUsingSemaphore {

    public static void main(String[] args) {

        PrintABCUsingSemaphore printABC = new PrintABCUsingSemaphore();
        new Thread(() -> printABC.printA()).start();
        new Thread(() -> printABC.printB()).start();
        new Thread(() -> printABC.printC()).start();
    }
}

class PrintABCUsingSemaphore {

    private Semaphore semaphoreA = new Semaphore(1);
    private Semaphore semaphoreB = new Semaphore(0);
    private Semaphore semaphoreC = new Semaphore(0);

    private final int TIMES = 5; //順序打印次數

    public void printA() {
        for (int i = 0; i < TIMES; i++) {
            print("A", semaphoreA, semaphoreB);
        }
    }

    public void printB() {
        for (int i = 0; i < TIMES; i++) {
            print("B", semaphoreB, semaphoreC);
        }
    }

    public void printC() {
        for (int i = 0; i < TIMES; i++) {
            print("C", semaphoreC, semaphoreA);
        }

    }

    private void print(String name, Semaphore currentSemaphore, Semaphore nextSemaphore) {
        try {
            currentSemaphore.acquire(1); // currentSemaphore獲取1個許可，如果沒有就阻塞
            System.out.println(Thread.currentThread().getName() + " print " + name);
            nextSemaphore.release(1); //歸還1個許可給nextSemaphore
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}