java queue队列demo
1.ArrayBlockingQueue:基于数组实现的一个阻塞队列,在创建ArrayBlockingQueue对象时必须制定容量大小。并且可以指定公平性与非公平性,默认情况下为非公平的,即不保证等待时间最长的队列最优先能够访问队列。
2.ArrayBlockingQueue内部通过Object[]数组保存数据的,也就是说ArrayBlockingQueue本质上是通过数组实现的。ArrayBlockingQueue的大小,即数组的容量是在创建创建ArrayBlockingQueue时候指定的。
3.如下图所示,ArrayBlockingQueue和ReentrantLock是组合关系,ArrayBlockingQueue中包含一个ReentrantLock对象。ReentrantLock是可重入的互斥锁。ArrayBlockingQueue就是根据ReentrantLock互斥锁实现"多线程对共享资源的访问"。
ReentrantLock分为公平锁和非公平锁,关于具体使用公平锁还是非公平锁,在创建ArrayBlockingQueue时可以指定; 而且ArrayBlockingQueue默认会使用非公平锁。
4.ArrayBlockingQueue和Condition是组合关系,ArrayBlockingQueue中包含两个Condition对象(notEmpty和notFull)。使用通知模式实现:所谓通知模式,当生产者往满的队列里面添加元素的时候,会阻塞生产者(调用Condition notFull.await()进行等待);
当消费者消费了一个队列中的元素后,会通知(调用Condition notFull.signal()唤醒生产者)生产者当前队列可用。反之,当消费者消费的时候,发现队列是空的,则消费者会被阻塞(通过Condition的 notEmpty.await()进行等待),
当生产者插入了队列中的一个元素后,则会调用notEmpty.signal()唤醒消费者继续消费。
package com.demo.zlearn.queue; import java.util.concurrent.ArrayBlockingQueue; import java.util.concurrent.BlockingQueue; public class ArrayBlockingQueueDemo { public static void main(String[] args) throws Exception { BlockingQueue queue = new ArrayBlockingQueue(5,true); Producer producer = new Producer(queue); Consumer consumer1 = new Consumer(queue,1000); new Thread(producer).start(); new Thread(consumer1).start(); } } class Producer implements Runnable{ protected BlockingQueue queue = null; public Producer(BlockingQueue queue) { this.queue = queue; } public void run() { try { for(int i=0;i<10;i++){ System.out.println("put:"+i); queue.put("AA"); Thread.sleep(4000); } } catch (InterruptedException e) { e.printStackTrace(); } } } class Consumer implements Runnable{ protected BlockingQueue queue = null; private long sleepTimes = 0; public Consumer(BlockingQueue queue,long sleepTimes) { this.queue = queue; this.sleepTimes = sleepTimes; } public void run() { try { while(true){ System.out.println("isEmpty:"+queue.isEmpty()+"\n"+ "size:"+queue.size()+"\n"+ "remainingCapacity:"+queue.remainingCapacity()+"\n" + "take:"+queue.take()+"\n"+ "sleepTimes:"+sleepTimes); //take 如果队列为空,则阻塞 System.out.println("-----------------------"); Thread.sleep(sleepTimes); } } catch (InterruptedException e) { e.printStackTrace(); } } }
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put:0
isEmpty:true
size:0
remainingCapacity:5
take:AA
sleepTimes:1000
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put:1
isEmpty:true
size:0
remainingCapacity:5
take:AA
sleepTimes:1000
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put:2
isEmpty:true
size:0
remainingCapacity:5
take:AA
sleepTimes:1000
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put:3
isEmpty:true
size:0
remainingCapacity:5
take:AA
sleepTimes:1000
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