Java多線程：用三個線程控制循環輸出10次ABC

題目：有A,B,C三個線程, A線程輸出A, B線程輸出B, C線程輸出C，要求, 同時啟動三個線程, 按順序輸出ABC, 循環10次。

解題思路：要按順序輸出ABC, 循環10次，就要控制三個線程同步工作，也就是說要讓三個線程輪流輸出，直到10個ABC全部輸出則結束線程。這里用一個Lock對象來控制三個線程的同步。用一個int型變量state標識由那個線程輸出。

 

package com.thread;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class ABC {
    private static int state = 0;

    public static void main(String[] args) {
        final Lock l = new ReentrantLock();
        
        Thread A = new Thread(new Runnable(){
            @Override
            public void run() {
                while (state<=30) {
                    l.lock();
                    if(state%3==0){
                        System.out.println("A");
                        state ++;
                    }
                    l.unlock();
                }
            }
        });
        Thread B = new Thread(new Runnable(){
            @Override
            public void run() {
                while (state<=30) {
                    l.lock();
                    if(state%3==1){
                        System.out.println("B");
                        state ++;
                    }
                    l.unlock();
                }
            }
        });
        Thread C = new Thread(new Runnable(){

            @Override
            public void run() {
                while (state<=30) {
                    l.lock();
                    if(state%3==2){
                        System.out.println("C");
                        state ++;
                    }
                    l.unlock();
                }
            }
        });
        A.start();
        B.start();
        C.start();
    }

}

運行結果：
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C