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JUC 之 BlockingQueue 接口以及 ArrayBlockingQueue 實(shí)現(xiàn)類詳解

猿友 2020-08-11 16:23:23 瀏覽數(shù) (3319)
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隊(duì)列是一種 FIFO（先進(jìn)先出）的數(shù)據(jù)結(jié)構(gòu)，本文要講的 BlockingQueue 也是一種隊(duì)列，而且強(qiáng)調(diào)了線程安全的特性。

BlockingQueue全稱：java.util.concurrent.BlockingQueue。它是是一個(gè)線程安全的隊(duì)列接口，多個(gè)線程能夠以并發(fā)的方式從隊(duì)列中插入數(shù)據(jù)，取出數(shù)據(jù)的同時(shí)不會(huì)出現(xiàn)線程安全的問(wèn)題。

生產(chǎn)者和消費(fèi)者例子

BlockingQueue 通常用于消費(fèi)者線程向隊(duì)列存入數(shù)據(jù)，消費(fèi)者線程從隊(duì)列中取出數(shù)據(jù)，具體如下

消費(fèi)者線程

  1. 生產(chǎn)者線程不停的向隊(duì)列中插入數(shù)據(jù)，直到隊(duì)列滿了，生產(chǎn)者線程被阻塞
  2. 消費(fèi)者線程不停的從隊(duì)列中取出數(shù)據(jù)，直到隊(duì)列為空，消費(fèi)者線程被阻塞

(推薦教程：Java教程）

BlockingQueue 方法

BlockingQueue 提供 4 種不同類型的方法用于插入數(shù)，取出數(shù)據(jù)以及檢查數(shù)據(jù)，具體如下

  1. 操作失敗，拋出異常
  2. 無(wú)論成功/失敗，立即返回 true/false
  3. 如果隊(duì)列為空/滿，阻塞當(dāng)前線程
  4. 如果隊(duì)列為空/滿，阻塞當(dāng)前線程并有超時(shí)機(jī)制插入add(o) offer(o) put(o) offer(o, timeout, timeunit)取出remove(o) poll() take() poll(timeout, timeunit)檢查element() peek()

BlockingQueue 的具體實(shí)現(xiàn)類

BlockingQueue 只是一個(gè)接口，在實(shí)際開(kāi)發(fā)中有如下的類實(shí)現(xiàn)了該接口。

  1. ArrayBlockingQueue
  2. DelayQueue
  3. LinkedBlockingQueue
  4. PriorityBlockingQueue
  5. SynchronousQueue

ArrayBlockingQueue 的使用

BlockingQueue 接口

這里以 BlockingQueue 接口的具體實(shí)現(xiàn)類 ArrayBlockingQueue 舉例。通過(guò) ArrayBlockingQueue實(shí)現(xiàn)一個(gè)消費(fèi)者和生產(chǎn)者多線程模型。

核心內(nèi)容如下：

  1. 以 ArrayBlockingQueue 作為生產(chǎn)者和消費(fèi)者的數(shù)據(jù)容器
  2. 通過(guò) ExecutorService 啟動(dòng) 3 個(gè)線程，2 兩個(gè)生產(chǎn)者，1 個(gè)消費(fèi)者
  3. 指定數(shù)據(jù)總量

（推薦微課：Java微課）

生產(chǎn)者線程

ArrayBlockingQueueProducer

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.atomic.AtomicInteger;


/**
 * 生產(chǎn)者線程向容器存入指定總量的 任務(wù)
 *
 */
public class ArrayBlockingQueueProducer implements Runnable {


    private static final Logger logger = LoggerFactory.getLogger(ArrayBlockingQueueProducer.class);


    // 容器
    private ArrayBlockingQueue<String> queue;
    // 生產(chǎn)指定的數(shù)量
    private AtomicInteger numberOfElementsToProduce;


    public ArrayBlockingQueueProducer(ArrayBlockingQueue<String> queue, AtomicInteger numberOfElementsToProduce) {
        this.queue = queue;
        this.numberOfElementsToProduce = numberOfElementsToProduce;
    }


    @Override
    public void run() {
        try {
            while (numberOfElementsToProduce.get() > 0) {
                try {
                    // 向隊(duì)列中存入任務(wù)
                    String task = String.format("task_%s", numberOfElementsToProduce.getAndUpdate(x -> x-1));
                    queue.put(task);
                    logger.info("thread {}, produce task {}", Thread.currentThread().getName(), task);


                    // 任務(wù)為0，生產(chǎn)者線程退出
                    if (numberOfElementsToProduce.get() == 0) {
                        break;
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        } catch (Exception e) {
            logger.error(this.getClass().getName().concat(". has error"), e);
        }


    }
}

消費(fèi)者線程

ArrayBlockingQueueConsumer

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.atomic.AtomicInteger;


/**
 * 消費(fèi)者線程向容器 消費(fèi) 指定總量的任務(wù)
 *
 */
public class ArrayBlockingQueueConsumer implements Runnable {


    private static final Logger logger = LoggerFactory.getLogger(ArrayBlockingQueueConsumer.class);


    private ArrayBlockingQueue<String> queue;
    private AtomicInteger numberOfElementsToProduce;


    public ArrayBlockingQueueConsumer(ArrayBlockingQueue<String> queue, AtomicInteger numberOfElementsToProduce) {
        this.queue = queue;
        this.numberOfElementsToProduce = numberOfElementsToProduce;
    }


    @Override
    public void run() {
        try {
            while (!queue.isEmpty() || numberOfElementsToProduce.get() >= 0) {
                // 從隊(duì)列中獲取任務(wù)，并執(zhí)行任務(wù)
                String task = queue.take();
                logger.info("thread {} consume task {}", Thread.currentThread().getName(),task);


                // 隊(duì)列中數(shù)據(jù)為空，消費(fèi)者線程退出
                if (queue.isEmpty()) {
                    break;
                }
            }
        } catch (Exception e) {
            logger.error(this.getClass().getName().concat(". has error"), e);
        }
    }
}

測(cè)試 TestBlockingQueue

import com.ckjava.synchronizeds.appCache.WaitUtils;


import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicInteger;


/**
 * 1. 以 ArrayBlockingQueue 作為生產(chǎn)者和消費(fèi)者的數(shù)據(jù)容器 <br>
 * 2. 通過(guò) ExecutorService 啟動(dòng) 3 個(gè)線程，2 兩個(gè)生產(chǎn)者，1 個(gè)消費(fèi)者 <br>
 * 3. 指定數(shù)據(jù)總量
 */
public class TestBlockingQueue {
    public static void main(String[] args) {
        ArrayBlockingQueue<String> arrayBlockingQueue = new ArrayBlockingQueue<>(10);
        /*BlockingQueue delayQueue = new DelayQueue();
        BlockingQueue<String> linkedBlockingQueue = new LinkedBlockingQueue<>(10);
        BlockingQueue<String> priorityBlockingQueue = new PriorityBlockingQueue<>(10);
        BlockingQueue<String> synchronousQueue = new SynchronousQueue<>();*/


        ExecutorService executorService = Executors.newFixedThreadPool(3);
        // 最多生產(chǎn) 5 個(gè)數(shù)據(jù)
        AtomicInteger numberOfElementsToProduce = new AtomicInteger(5);


        // 2 個(gè)生產(chǎn)者線程
        executorService.submit(new ArrayBlockingQueueProducer(arrayBlockingQueue, numberOfElementsToProduce));
        executorService.submit(new ArrayBlockingQueueProducer(arrayBlockingQueue, numberOfElementsToProduce));
        // 1 個(gè)消費(fèi)者線程
        executorService.submit(new ArrayBlockingQueueConsumer(arrayBlockingQueue, numberOfElementsToProduce));


        executorService.shutdown();
        WaitUtils.waitUntil(() -> executorService.isTerminated(), 1000L);
    }
}

輸出如下：

13:54:17.884 [pool-1-thread-3] INFO  c.c.b.ArrayBlockingQueueConsumer - thread pool-1-thread-3 consume task task_5
13:54:17.884 [pool-1-thread-1] INFO  c.c.b.ArrayBlockingQueueProducer - thread pool-1-thread-1, produce task task_5
13:54:17.884 [pool-1-thread-2] INFO  c.c.b.ArrayBlockingQueueProducer - thread pool-1-thread-2, produce task task_4
13:54:17.887 [pool-1-thread-3] INFO  c.c.b.ArrayBlockingQueueConsumer - thread pool-1-thread-3 consume task task_4
13:54:17.887 [pool-1-thread-2] INFO  c.c.b.ArrayBlockingQueueProducer - thread pool-1-thread-2, produce task task_2
13:54:17.887 [pool-1-thread-1] INFO  c.c.b.ArrayBlockingQueueProducer - thread pool-1-thread-1, produce task task_3
13:54:17.887 [pool-1-thread-3] INFO  c.c.b.ArrayBlockingQueueConsumer - thread pool-1-thread-3 consume task task_3
13:54:17.887 [pool-1-thread-2] INFO  c.c.b.ArrayBlockingQueueProducer - thread pool-1-thread-2, produce task task_1
13:54:17.887 [pool-1-thread-3] INFO  c.c.b.ArrayBlockingQueueConsumer - thread pool-1-thread-3 consume task task_2
13:54:17.887 [pool-1-thread-3] INFO  c.c.b.ArrayBlockingQueueConsumer - thread pool-1-thread-3 consume task task_1

（推薦內(nèi)容：Java面試基礎(chǔ)題）

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