廖雪峰Java11多线程编程-3高级concurrent包-3Condition

最新推荐文章于 2025-09-10 15:58:35 发布

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最新推荐文章于 2025-09-10 15:58:35 发布

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文章标签： java

原文链接：http://www.cnblogs.com/csj2018/p/11013173.html

本文深入探讨了Java中Condition机制的使用，展示了如何利用ReentrantLock和Condition对象替代传统的synchronized关键字及wait/notify方法，实现更灵活的线程间同步。通过具体示例，解释了Condition的await、signal和signalAll方法的工作原理。

Condition实现等待和唤醒线程

java.util.locks.ReentrantLock用于替代synchronized加锁

synchronized可以使用wait和notify实现在条件不满足时的等待，条件满足时的唤醒。

class TaskQueue{
    final Lock lock = new ReentrantLock()
    final Condition notEmpty = lock.newCondition();
}

使用Condition对象可以通过await和signal实现条件不满足时的等待，条件满足时的唤醒

Condition.await/signal/signalAll原理和wait/notify/notifyAll一致

await()会释放当前锁，进入等待状态
signal()会唤醒某个等待线程
signalAll()会唤醒所有等待线程
唤醒线程从await()返回后需要重新获得锁

import java.util.LinkedList;
import java.util.Queue;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

class TaskQueue{
    final Queue<String> queue = new LinkedList<>();
    final Lock lock = new ReentrantLock();
    final Condition notEmpty = lock.newCondition();
    public String getTask() throws InterruptedException{
        lock.lock();
        try{
            while(this.queue.isEmpty()){
                notEmpty.await();
            }
            return queue.remove();
        }finally {
            lock.unlock();
        }
    }
    public void addTask(String name){
        lock.lock();
        try{
            this.queue.add(name);
            notEmpty.signalAll();
        }finally {
            lock.unlock();
        }
    }
}
class WorkerThread extends Thread{
    TaskQueue taskQueue;
    public WorkerThread(TaskQueue taskQueue){
        this.taskQueue = taskQueue;
    }
    public void run(){
        while(!isInterrupted()){
            String name;
            try{
                name = taskQueue.getTask();
            }catch (InterruptedException e){
                break;
            }
            String result = "Hello, "+name+" !";
            System.out.println(result);
        }
    }
}
public class Main{
    public static void main(String[] args) throws InterruptedException{
        TaskQueue taskQueue = new TaskQueue();
        WorkerThread worker = new WorkerThread(taskQueue);
        worker.start();
        taskQueue.addTask("Bob");
        Thread.sleep(1000);
        taskQueue.addTask("Alice");
        Thread.sleep(1000);
        taskQueue.addTask("Tim");
        Thread.sleep(1000);
        worker.interrupt();
        worker.join();
        System.out.println("END");
    }
}