• 并发控制-条件对象(Condition接口)


    在并发控制的流程中,有一个很重要的概念,即为标题中的条件对象,条件对象对应的英文是Condition接口,我们使用ReentrantLock是,发现基于ReentrantLock可以获取到Contition接口,可以进行阻塞或者唤醒操作。本文从以下几个方面介绍。

    Condition作用及用途

      Condition是基于ReentrantLock使用的,我们使用Condition可以实现条件判断

    Condition代码演示

      演示代码1

        演示Condition的基本用法,如下代码所示:

        

    package com.yang.concurrent;
    
    import java.util.concurrent.locks.Condition;
    import java.util.concurrent.locks.ReentrantLock;
    
    /**
     * 本实例测试Condition的基本用法
     */
    public class ConditionDemo1 {
        private ReentrantLock reentrantLock=new ReentrantLock();
        private Condition condition=reentrantLock.newCondition();
    
        public static void main(String[] args) {
            ConditionDemo1 conditionDemo1 = new ConditionDemo1();
            new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        Thread.sleep(1000);
                        conditionDemo1.method2();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }).start();
            conditionDemo1.method1();
        }
    
        public void method1(){
            reentrantLock.lock();
            try {
                System.out.println("条件不满足,等待中");
                condition.await();
                System.out.println("条件满足,可以运行");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }finally {
                reentrantLock.unlock();
            }
        }
    
        public void method2(){
            reentrantLock.lock();
            try{
                condition.signal();
                System.out.println("条件转换为满足");
            }finally {
                reentrantLock.unlock();
            }
        }
    }
    

        运行结果如下:

        

      演示代码2

        本代码演示用Condition实现生产者和消费者,如下实例代码所示

        

    package com.yang.concurrent;
    
    import java.util.PriorityQueue;
    import java.util.concurrent.locks.Condition;
    import java.util.concurrent.locks.ReentrantLock;
    
    /**
     * 此实例我们用Condition去模拟生产者和消费者的实现
     */
    public class ConditionDemo2 {
        private int queueSize = 10;
        private PriorityQueue<Integer> queue = new PriorityQueue<Integer>(10);
        private ReentrantLock reentrantLock = new ReentrantLock();
        private Condition notFull = reentrantLock.newCondition();
        private Condition notEmpty = reentrantLock.newCondition();
    
        public static void main(String[] args) {
            ConditionDemo2 conditionDemo2 = new ConditionDemo2();
    
            Provider provider = conditionDemo2.new Provider();
            Consumer consumer=conditionDemo2.new Consumer();
            provider.start();
            consumer.start();
        }
    
        class Provider extends Thread {
            @Override
            public void run() {
                provid();
            }
    
            private void provid() {
                while (true) {
                    reentrantLock.lock();
                    try {
                        //一直在生产
                        while (queue.size() == queueSize) {
                            try {
                                System.out.println("队列满了,等待中");
                                notFull.await();
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                        }
                        queue.offer(1);
                        notEmpty.signalAll();
                        System.out.println("对列中放入了一个数据,队列大小为:" + queue.size());
    
                    } finally {
                        reentrantLock.unlock();
                    }
                }
            }
        }
    
        class Consumer extends Thread {
            @Override
            public void run() {
                consume();
            }
    
            private void consume() {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                //一直在消费
                while (true) {
    
    
                    reentrantLock.lock();
                    try {
    
                        while (queue.size() == 0) {
                            //队列空
                            System.out.println("队列为空,等待中");
                            try {
                                notEmpty.await();
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                        }
                        queue.poll();
                        notFull.signalAll();
                        System.out.println("从队列中取走了一个数据,队列剩余:" + queue.size());
                    } finally {
                        reentrantLock.unlock();
                    }
                }
            }
        }
    
    }
    

       运行结果如下图所示:

      

    Condition使用说明

       当我们调用await方法后,就释放了锁

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  • 原文地址:https://www.cnblogs.com/cnxieyang/p/12774829.html
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