目录
- 方法一：使用synchronized和wait/notify
- 方法二：使用`CompletableFuture`实现
方法一：使用synchronized和wait/notify
package com.demo;
import java.util.concurrent.CompletableFuture;
public class PrintABC {
// 当前状态
private static String state = "A";
// 共享锁对象
private static final Object lock = new Object();
public static void main(String[] args) {
Thread t1 = new Thread(() -> {
synchronized (lock){
System.out.println("current: A; state: " + state);
// 等待
while (!"A".equals(state)){
try {
lock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println("A: " + Thread.currentThread());
// 修改B状态
state = "B";
// 唤醒下一个
lock.notifyAll();
}
});
Thread t2 = new Thread(() -> {
synchronized (lock){
System.out.println("current: B; state: " + state);
// 等待
while (!"B".equals(state)){
try {
lock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println("B: " + Thread.currentThread());
// 修改B状态
state = "C";
// 唤醒下一个
lock.notifyAll();
}
});
Thread t3 = new Thread(() -> {
synchronized (lock){
System.out.println("current: C; state: " + state);
// 等待
while (!"C".equals(state)){
try {
lock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println("C: " + Thread.currentThread());
// 修改B状态
state = "";
// 唤醒下一个
lock.notifyAll();
}
});
t1.start();
t2.start();
t3.start();
}
}输出
current: A; state: A
A: Thread[Thread-0,5,main]
current: C; state: B
current: B; state: B
B: Thread[Thread-1,5,main]
C: Thread[Thread-2,5,main]方法二：使用CompletableFuture实现
package com.demo;
import java.util.concurrent.CompletableFuture;
public class PrintABC {
public static void main(String[] args) {
CompletableFuture<Void> t1 = CompletableFuture.runAsync(() -> {
System.out.println("A: " + Thread.currentThread());
});
CompletableFuture<Void> t2 = t1.thenRunAsync(() -> {
System.out.println("B: " + Thread.currentThread());
});
t2.thenRunAsync(()->{
System.out.println("C: " + Thread.currentThread());
});
}
}输出
A: Thread[ForkJoinPool.commonPool-worker-1,5,main]
B: Thread[ForkJoinPool.commonPool-worker-1,5,main]
C: Thread[ForkJoinPool.commonPool-worker-2,5,main]参考
华为OD面试：三个线程交替打印ABC如何实现？面试题：三个线程如何交替打印ABC100次
