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class="sidebar-group"><button class="sidebar-heading clickable active"><!----><span class="title">2.11 并发编程</span><span class="arrow down"></span></button><ul class="sidebar-links"><li><!--[--><a href="/thread/wangzhe-thread.html" class="nav-link sidebar-link sidebar-page" aria-label="创建Java线程的3种方式"><!---->创建Java线程的3种方式<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/thread-state-and-method.html" class="nav-link sidebar-link sidebar-page" aria-label="线程的6种状态及切换"><!---->线程的6种状态及切换<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/thread-group-and-thread-priority.html" class="nav-link sidebar-link sidebar-page" aria-label="线程组和线程优先级"><!---->线程组和线程优先级<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/why-need-thread.html" class="nav-link sidebar-link sidebar-page" aria-label="进程与线程的区别"><!---->进程与线程的区别<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/thread-bring-some-problem.html" class="nav-link sidebar-link sidebar-page" aria-label="并发编程带来了哪些问题"><!---->并发编程带来了哪些问题<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/jmm.html" class="nav-link sidebar-link sidebar-page" aria-label="Java内存模型"><!---->Java内存模型<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/volatile.html" class="nav-link sidebar-link sidebar-page" aria-label="volatile"><!---->volatile<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/synchronized.html" class="nav-link sidebar-link sidebar-page" aria-label="synchronized"><!---->synchronized<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/cas.html" class="nav-link sidebar-link sidebar-page" aria-label="CAS的原理"><!---->CAS的原理<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/aqs.html" class="nav-link sidebar-link sidebar-page" aria-label="AQS详解"><!---->AQS详解<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/lock.html" class="nav-link sidebar-link sidebar-page" aria-label="锁"><!---->锁<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/reentrantLock.html" class="nav-link sidebar-link sidebar-page" aria-label="重入锁ReentrantLock"><!---->重入锁ReentrantLock<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/ReentrantReadWriteLock.html" class="nav-link sidebar-link sidebar-page" aria-label="读写锁ReentrantReadWriteLock"><!---->读写锁ReentrantReadWriteLock<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/condition.html" class="nav-link sidebar-link sidebar-page" aria-label="线程协作类Condition"><!---->线程协作类Condition<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/LockSupport.html" class="nav-link sidebar-link sidebar-page" aria-label="线程阻塞唤醒类LockSupport"><!---->线程阻塞唤醒类LockSupport<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/map.html" class="nav-link sidebar-link sidebar-page" aria-label="并发集合容器"><!---->并发集合容器<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/ConcurrentHashMap.html" class="nav-link sidebar-link sidebar-page" aria-label="ConcurrentHashMap"><!---->ConcurrentHashMap<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/ConcurrentLinkedQueue.html" class="nav-link sidebar-link sidebar-page" aria-label="ConcurrentLinkedQueue"><!---->ConcurrentLinkedQueue<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/CopyOnWriteArrayList.html" class="nav-link sidebar-link sidebar-page" aria-label="CopyOnWriteArrayList"><!---->CopyOnWriteArrayList<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/ThreadLocal.html" class="nav-link sidebar-link sidebar-page" aria-label="ThreadLocal"><!---->ThreadLocal<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a aria-current="page" href="/thread/BlockingQueue.html" class="router-link-active router-link-exact-active nav-link active sidebar-link sidebar-page active" aria-label="BlockingQueue"><!---->BlockingQueue<!----></a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header"><a aria-current="page" href="/thread/BlockingQueue.html#基本操作" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="基本操作"><!---->基本操作<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/thread/BlockingQueue.html#常用的blockingqueue" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="常用的BlockingQueue"><!---->常用的BlockingQueue<!----></a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header"><a aria-current="page" href="/thread/BlockingQueue.html#arrayblockingqueue" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="ArrayBlockingQueue"><!---->ArrayBlockingQueue<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/thread/BlockingQueue.html#linkedblockingqueue" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="LinkedBlockingQueue"><!---->LinkedBlockingQueue<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/thread/BlockingQueue.html#priorityblockingqueue" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="PriorityBlockingQueue"><!---->PriorityBlockingQueue<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/thread/BlockingQueue.html#synchronousqueue" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="SynchronousQueue"><!---->SynchronousQueue<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/thread/BlockingQueue.html#linkedtransferqueue" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="LinkedTransferQueue"><!---->LinkedTransferQueue<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/thread/BlockingQueue.html#linkedblockingdeque" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="LinkedBlockingDeque"><!---->LinkedBlockingDeque<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/thread/BlockingQueue.html#delayqueue" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="DelayQueue"><!---->DelayQueue<!----></a><ul class="sidebar-sub-headers"></ul></li></ul></li></ul><!--]--></li><li><!--[--><a href="/thread/pool.html" class="nav-link sidebar-link sidebar-page" aria-label="线程池"><!---->线程池<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/ScheduledThreadPoolExecutor.html" class="nav-link sidebar-link sidebar-page" aria-label="计划任务"><!---->计划任务<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/atomic.html" class="nav-link sidebar-link sidebar-page" aria-label="原子操作类"><!---->原子操作类<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/CountDownLatch.html" class="nav-link sidebar-link sidebar-page" aria-label="通信工具类CountDownLatch"><!---->通信工具类CountDownLatch<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/fork-join.html" class="nav-link sidebar-link sidebar-page" aria-label="Fork/Join框架"><!---->Fork/Join框架<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/thread/shengchanzhe-xiaofeizhe.html" class="nav-link sidebar-link sidebar-page" aria-label="生产者-消费者模式"><!---->生产者-消费者模式<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li></ul></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">2.12 JVM</span><span class="arrow right"></span></button><!----></section><!--]--></li></ul></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">三、Java企业级开发</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">四、数据库</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">五、计算机基础</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">六、求职面试</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">七、学习资源</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">八、知识库搭建</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">九、联系作者</span><span class="arrow right"></span></button><!----></section><!--]--></li></ul><!--[--><!----><!--]--></aside><!--[--><main class="page" id="main-content"><!--[--><!----><nav class="breadcrumb disable"></nav><div class="page-title"><h1><!---->吊打Java并发面试官之BlockingQueue</h1><div class="page-info"><span class="author-info" aria-label="作者🖊" data-balloon-pos="down" isoriginal="false" pageview="false"><svg xmlns="http://www.w3.org/2000/svg" class="icon author-icon" viewbox="0 0 1024 1024" fill="currentColor" aria-label="author icon"><path d="M649.6 633.6c86.4-48 147.2-144 147.2-249.6 0-160-128-288-288-288s-288 128-288 288c0 108.8 57.6 201.6 147.2 249.6-121.6 48-214.4 153.6-240 288-3.2 9.6 0 19.2 6.4 25.6 3.2 9.6 12.8 12.8 22.4 12.8h704c9.6 0 19.2-3.2 25.6-12.8 6.4-6.4 9.6-16 6.4-25.6-25.6-134.4-121.6-240-243.2-288z"></path></svg><span><a class="author-item" href="https://tobebetterjavaer.com" target="_blank" rel="noopener noreferrer">沉默王二</a></span><span property="author" content="沉默王二"></span></span><!----><span class="date-info" aria-label="写作日期📅" data-balloon-pos="down" isoriginal="false" pageview="false"><svg xmlns="http://www.w3.org/2000/svg" class="icon calendar-icon" viewbox="0 0 1024 1024" fill="currentColor" aria-label="calendar icon"><path d="M716.4 110.137c0-18.753-14.72-33.473-33.472-33.473-18.753 0-33.473 14.72-33.473 33.473v33.473h66.993v-33.473zm-334.87 0c0-18.753-14.72-33.473-33.473-33.473s-33.52 14.72-33.52 33.473v33.473h66.993v-33.473zm468.81 33.52H716.4v100.465c0 18.753-14.72 33.473-33.472 33.473a33.145 33.145 0 01-33.473-33.473V143.657H381.53v100.465c0 18.753-14.72 33.473-33.473 33.473a33.145 33.145 0 01-33.473-33.473V143.657H180.6A134.314 134.314 0 0046.66 277.595v535.756A134.314 134.314 0 00180.6 947.289h669.74a134.36 134.36 0 00133.94-133.938V277.595a134.314 134.314 0 00-133.94-133.938zm33.473 267.877H147.126a33.145 33.145 0 01-33.473-33.473c0-18.752 14.72-33.473 33.473-33.473h736.687c18.752 0 33.472 14.72 33.472 33.473a33.145 33.145 0 01-33.472 33.473z"></path></svg><span>2022年3月23日</span><meta property="datePublished" content="2022-03-23T12:08:58.000Z"></span><span class="category-info" aria-label="分类🌈" data-balloon-pos="down" isoriginal="false" pageview="false"><svg xmlns="http://www.w3.org/2000/svg" class="icon category-icon" viewbox="0 0 1024 1024" fill="currentColor" aria-label="category icon"><path d="M148.41 106.992h282.176c22.263 0 40.31 18.048 40.31 40.31V429.48c0 22.263-18.047 40.31-40.31 40.31H148.41c-22.263 0-40.311-18.047-40.311-40.31V147.302c0-22.263 18.048-40.31 40.311-40.31zM147.556 553.478H429.73c22.263 0 40.311 18.048 40.311 40.31v282.176c0 22.263-18.048 40.312-40.31 40.312H147.555c-22.263 0-40.311-18.049-40.311-40.312V593.79c0-22.263 18.048-40.311 40.31-40.311zM593.927 106.992h282.176c22.263 0 40.31 18.048 40.31 40.31V429.48c0 22.263-18.047 40.31-40.31 40.31H593.927c-22.263 0-40.311-18.047-40.311-40.31V147.302c0-22.263 18.048-40.31 40.31-40.31zM730.22 920.502H623.926c-40.925 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19.03v5.825h566.49v-5.825c0-7.379-2.849-13.981-7.509-18.9-5.049-193.016-97.867-351.985-220.2-389.527 123.24-37.67 216.446-198.453 220.588-392.892zM531.16 450.445v352.632c117.674 1.553 211.787 40.778 211.787 88.676H304.097c0-48.286 95.149-87.382 213.728-88.676V450.445c-93.077-3.107-167.901-81.297-167.901-177.093 0-8.803 6.99-15.793 15.793-15.793 8.803 0 15.794 6.99 15.794 15.793 0 80.261 63.69 145.635 142.01 145.635s142.011-65.374 142.011-145.635c0-8.803 6.99-15.793 15.794-15.793s15.793 6.99 15.793 15.793c0 95.019-73.789 172.82-165.96 177.093z"></path></svg><span>大约 12 分钟</span><meta property="timeRequired" content="PT12M"></span></div><hr></div><div class="toc-place-holder"><aside id="toc"><div class="toc-header">此页内容</div><div class="toc-wrapper"><ul class="toc-list"><!--[--><li class="toc-item"><a aria-current="page" href="/thread/BlockingQueue.html#基本操作" class="router-link-active router-link-exact-active toc-link level2">基本操作</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/thread/BlockingQueue.html#常用的blockingqueue" class="router-link-active router-link-exact-active toc-link level2">常用的BlockingQueue</a></li><ul class="toc-list"><!--[--><li class="toc-item"><a aria-current="page" href="/thread/BlockingQueue.html#arrayblockingqueue" class="router-link-active router-link-exact-active toc-link level3">ArrayBlockingQueue</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/thread/BlockingQueue.html#linkedblockingqueue" class="router-link-active router-link-exact-active toc-link level3">LinkedBlockingQueue</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/thread/BlockingQueue.html#priorityblockingqueue" class="router-link-active router-link-exact-active toc-link level3">PriorityBlockingQueue</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/thread/BlockingQueue.html#synchronousqueue" class="router-link-active router-link-exact-active toc-link level3">SynchronousQueue</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/thread/BlockingQueue.html#linkedtransferqueue" class="router-link-active router-link-exact-active toc-link level3">LinkedTransferQueue</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/thread/BlockingQueue.html#linkedblockingdeque" class="router-link-active router-link-exact-active toc-link level3">LinkedBlockingDeque</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/thread/BlockingQueue.html#delayqueue" class="router-link-active router-link-exact-active toc-link level3">DelayQueue</a></li><!----><!--]--></ul><!--]--></ul></div></aside></div><!----><div class="theme-hope-content"><p>最常用的&quot;<strong>生产者-消费者</strong>&quot;问题中，队列通常被视作线程间操作的数据容器，这样，可以对各个模块的业务功能进行解耦，生产者将“生产”出来的数据放置在数据容器中，而消费者仅仅只需要在“数据容器”中进行获取数据即可，这样生产者线程和消费者线程就能够进行解耦，只专注于自己的业务功能即可。</p><p>阻塞队列（BlockingQueue）被广泛使用在“生产者-消费者”问题中，其原因是BlockingQueue提供了可阻塞的插入和移除的方法。<strong>当队列容器已满，生产者线程会被阻塞，直到队列未满；当队列容器为空时，消费者线程会被阻塞，直至队列非空时为止</strong>。</p><h2 id="基本操作" tabindex="-1"><a class="header-anchor" href="#基本操作" aria-hidden="true">#</a> 基本操作</h2><p>BlockingQueue基本操作总结如下（此图来源于JAVA API文档）：</p><p><img src="http://cdn.tobebetterjavaer.com/tobebetterjavaer/images/thread/BlockingQueue-01.png" alt=""></p><p>BlockingQueue继承于Queue接口，因此，对数据元素的基本操作有：</p><p>1）插入元素</p><ol><li>add(E e) ：往队列插入数据，当队列满时，插入元素时会抛出IllegalStateException异常；</li><li>offer(E e)：当往队列插入数据时，插入成功返回<code>true</code>，否则则返回<code>false</code>。当队列满时不会抛出异常；</li></ol><p>2）删除元素</p><ol><li>remove(Object o)：从队列中删除数据，成功则返回<code>true</code>，否则为<code>false</code></li><li>poll：删除数据，当队列为空时，返回null；</li></ol><p>3）查看元素</p><ol><li>element：获取队头元素，如果队列为空时则抛出NoSuchElementException异常；</li><li>peek：获取队头元素，如果队列为空则抛出NoSuchElementException异常</li></ol><p>BlockingQueue具有的特殊操作：</p><p>1）插入数据：</p><ol><li>put：当阻塞队列容量已经满时，往阻塞队列插入数据的线程会被阻塞，直至阻塞队列已经有空余的容量可供使用；</li><li><code>offer(E e, long timeout, TimeUnit unit)</code>：若阻塞队列已经满时，同样会阻塞插入数据的线程，直至阻塞队列已经有空余的地方，与put方法不同的是，该方法会有一个超时时间，若超过当前给定的超时时间，插入数据的线程会退出；</li></ol><p>2）删除数据</p><ol><li><code>take()</code>：当阻塞队列为空时，获取队头数据的线程会被阻塞；</li><li><code>poll(long timeout, TimeUnit unit)</code>：当阻塞队列为空时，获取数据的线程会被阻塞，另外，如果被阻塞的线程超过了给定的时长，该线程会退出</li></ol><h2 id="常用的blockingqueue" tabindex="-1"><a class="header-anchor" href="#常用的blockingqueue" aria-hidden="true">#</a> 常用的BlockingQueue</h2><p>实现BlockingQueue接口的有<code>ArrayBlockingQueue, DelayQueue, LinkedBlockingDeque, LinkedBlockingQueue, LinkedTransferQueue, PriorityBlockingQueue, SynchronousQueue</code>，而这几种常见的阻塞队列也是在实际编程中会常用的，下面对这几种常见的阻塞队列进行说明：</p><h3 id="arrayblockingqueue" tabindex="-1"><a class="header-anchor" href="#arrayblockingqueue" aria-hidden="true">#</a> ArrayBlockingQueue</h3><p><strong>ArrayBlockingQueue</strong>是由数组实现的有界阻塞队列。该队列命令元素FIFO（先进先出）。因此，对头元素时队列中存在时间最长的数据元素，而对尾数据则是当前队列最新的数据元素。ArrayBlockingQueue可作为“有界数据缓冲区”，生产者插入数据到队列容器中，并由消费者提取。ArrayBlockingQueue一旦创建，容量不能改变。</p><p>当队列容量满时，尝试将元素放入队列将导致操作阻塞;尝试从一个空队列中取一个元素也会同样阻塞。</p><p>ArrayBlockingQueue默认情况下不能保证线程访问队列的公平性，所谓公平性是指严格按照线程等待的绝对时间顺序，即最先等待的线程能够最先访问到ArrayBlockingQueue。而非公平性则是指访问ArrayBlockingQueue的顺序不是遵守严格的时间顺序，有可能存在，一旦ArrayBlockingQueue可以被访问时，长时间阻塞的线程依然无法访问到ArrayBlockingQueue。<strong>如果保证公平性，通常会降低吞吐量</strong>。如果需要获得公平性的ArrayBlockingQueue，可采用如下代码：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">private</span> <span class="token keyword">static</span> <span class="token class-name">ArrayBlockingQueue</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">Integer</span><span class="token punctuation">&gt;</span></span> blockingQueue <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ArrayBlockingQueue</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">Integer</span><span class="token punctuation">&gt;</span></span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">,</span><span class="token boolean">true</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>ArrayBlockingQueue的主要属性如下:</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token doc-comment comment">/** The queued items */</span>
<span class="token keyword">final</span> <span class="token class-name">Object</span><span class="token punctuation">[</span><span class="token punctuation">]</span> items<span class="token punctuation">;</span>

<span class="token doc-comment comment">/** items index for next take, poll, peek or remove */</span>
<span class="token keyword">int</span> takeIndex<span class="token punctuation">;</span>

<span class="token doc-comment comment">/** items index for next put, offer, or add */</span>
<span class="token keyword">int</span> putIndex<span class="token punctuation">;</span>

<span class="token doc-comment comment">/** Number of elements in the queue */</span>
<span class="token keyword">int</span> count<span class="token punctuation">;</span>

<span class="token comment">/*
 * Concurrency control uses the classic two-condition algorithm
 * found in any textbook.
 */</span>

<span class="token doc-comment comment">/** Main lock guarding all access */</span>
<span class="token keyword">final</span> <span class="token class-name">ReentrantLock</span> lock<span class="token punctuation">;</span>

<span class="token doc-comment comment">/** Condition for waiting takes */</span>
<span class="token keyword">private</span> <span class="token keyword">final</span> <span class="token class-name">Condition</span> notEmpty<span class="token punctuation">;</span>

<span class="token doc-comment comment">/** Condition for waiting puts */</span>
<span class="token keyword">private</span> <span class="token keyword">final</span> <span class="token class-name">Condition</span> notFull<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>从源码中可以看出ArrayBlockingQueue内部是采用数组进行数据存储的（<code>属性items</code>），为了保证线程安全，采用的是<code>ReentrantLock lock</code>，为了保证可阻塞式的插入删除数据利用的是Condition，当获取数据的消费者线程被阻塞时会将该线程放置到notEmpty等待队列中，当插入数据的生产者线程被阻塞时，会将该线程放置到notFull等待队列中。而notEmpty和notFull等中要属性在构造方法中进行创建：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">public</span> <span class="token class-name">ArrayBlockingQueue</span><span class="token punctuation">(</span><span class="token keyword">int</span> capacity<span class="token punctuation">,</span> <span class="token keyword">boolean</span> fair<span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span>capacity <span class="token operator">&lt;=</span> <span class="token number">0</span><span class="token punctuation">)</span>
        <span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token class-name">IllegalArgumentException</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">this</span><span class="token punctuation">.</span>items <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Object</span><span class="token punctuation">[</span>capacity<span class="token punctuation">]</span><span class="token punctuation">;</span>
    lock <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ReentrantLock</span><span class="token punctuation">(</span>fair<span class="token punctuation">)</span><span class="token punctuation">;</span>
    notEmpty <span class="token operator">=</span> lock<span class="token punctuation">.</span><span class="token function">newCondition</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    notFull <span class="token operator">=</span>  lock<span class="token punctuation">.</span><span class="token function">newCondition</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>接下来，主要看看可阻塞式的put和take方法是怎样实现的。</p><h4 id="_1-put方法详解" tabindex="-1"><a class="header-anchor" href="#_1-put方法详解" aria-hidden="true">#</a> 1）put方法详解</h4><p><code> put(E e)</code>方法源码如下：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">put</span><span class="token punctuation">(</span><span class="token class-name">E</span> e<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">InterruptedException</span> <span class="token punctuation">{</span>
    <span class="token function">checkNotNull</span><span class="token punctuation">(</span>e<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">final</span> <span class="token class-name">ReentrantLock</span> lock <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>lock<span class="token punctuation">;</span>
    lock<span class="token punctuation">.</span><span class="token function">lockInterruptibly</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">try</span> <span class="token punctuation">{</span>
		<span class="token comment">//如果当前队列已满，将线程移入到notFull等待队列中</span>
        <span class="token keyword">while</span> <span class="token punctuation">(</span>count <span class="token operator">==</span> items<span class="token punctuation">.</span>length<span class="token punctuation">)</span>
            notFull<span class="token punctuation">.</span><span class="token function">await</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
		<span class="token comment">//满足插入数据的要求，直接进行入队操作</span>
        <span class="token function">enqueue</span><span class="token punctuation">(</span>e<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span> <span class="token keyword">finally</span> <span class="token punctuation">{</span>
        lock<span class="token punctuation">.</span><span class="token function">unlock</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>该方法的逻辑很简单，当队列已满时（<code>count == items.length</code>）将线程移入到notFull等待队列中，如果当前满足插入数据的条件，就可以直接调用<code> enqueue(e)</code>插入数据元素。enqueue方法源码为：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">private</span> <span class="token keyword">void</span> <span class="token function">enqueue</span><span class="token punctuation">(</span><span class="token class-name">E</span> x<span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token comment">// assert lock.getHoldCount() == 1;</span>
    <span class="token comment">// assert items[putIndex] == null;</span>
    <span class="token keyword">final</span> <span class="token class-name">Object</span><span class="token punctuation">[</span><span class="token punctuation">]</span> items <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>items<span class="token punctuation">;</span>
	<span class="token comment">//插入数据</span>
    items<span class="token punctuation">[</span>putIndex<span class="token punctuation">]</span> <span class="token operator">=</span> x<span class="token punctuation">;</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">++</span>putIndex <span class="token operator">==</span> items<span class="token punctuation">.</span>length<span class="token punctuation">)</span>
        putIndex <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
    count<span class="token operator">++</span><span class="token punctuation">;</span>
	<span class="token comment">//通知消费者线程，当前队列中有数据可供消费</span>
    notEmpty<span class="token punctuation">.</span><span class="token function">signal</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>enqueue方法的逻辑同样也很简单，先完成插入数据，即往数组中添加数据（<code>items[putIndex] = x</code>），然后通知被阻塞的消费者线程，当前队列中有数据可供消费（<code>notEmpty.signal()</code>）。</p><h4 id="_2-take方法详解" tabindex="-1"><a class="header-anchor" href="#_2-take方法详解" aria-hidden="true">#</a> 2）take方法详解</h4><p>take方法源码如下：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">public</span> <span class="token class-name">E</span> <span class="token function">take</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">InterruptedException</span> <span class="token punctuation">{</span>
    <span class="token keyword">final</span> <span class="token class-name">ReentrantLock</span> lock <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>lock<span class="token punctuation">;</span>
    lock<span class="token punctuation">.</span><span class="token function">lockInterruptibly</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">try</span> <span class="token punctuation">{</span>
		<span class="token comment">//如果队列为空，没有数据，将消费者线程移入等待队列中</span>
        <span class="token keyword">while</span> <span class="token punctuation">(</span>count <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span>
            notEmpty<span class="token punctuation">.</span><span class="token function">await</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
		<span class="token comment">//获取数据</span>
        <span class="token keyword">return</span> <span class="token function">dequeue</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span> <span class="token keyword">finally</span> <span class="token punctuation">{</span>
        lock<span class="token punctuation">.</span><span class="token function">unlock</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>take方法也主要做了两步：</p><ol><li>如果当前队列为空的话，则将获取数据的消费者线程移入到等待队列中；</li><li>若队列不为空则获取数据，即完成出队操作<code>dequeue</code>。dequeue方法源码为：</li></ol><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">private</span> <span class="token class-name">E</span> <span class="token function">dequeue</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token comment">// assert lock.getHoldCount() == 1;</span>
    <span class="token comment">// assert items[takeIndex] != null;</span>
    <span class="token keyword">final</span> <span class="token class-name">Object</span><span class="token punctuation">[</span><span class="token punctuation">]</span> items <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>items<span class="token punctuation">;</span>
    <span class="token annotation punctuation">@SuppressWarnings</span><span class="token punctuation">(</span><span class="token string">&quot;unchecked&quot;</span><span class="token punctuation">)</span>
	<span class="token comment">//获取数据</span>
    <span class="token class-name">E</span> x <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token class-name">E</span><span class="token punctuation">)</span> items<span class="token punctuation">[</span>takeIndex<span class="token punctuation">]</span><span class="token punctuation">;</span>
    items<span class="token punctuation">[</span>takeIndex<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token keyword">null</span><span class="token punctuation">;</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">++</span>takeIndex <span class="token operator">==</span> items<span class="token punctuation">.</span>length<span class="token punctuation">)</span>
        takeIndex <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
    count<span class="token operator">--</span><span class="token punctuation">;</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span>itrs <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">)</span>
        itrs<span class="token punctuation">.</span><span class="token function">elementDequeued</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token comment">//通知被阻塞的生产者线程</span>
	notFull<span class="token punctuation">.</span><span class="token function">signal</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">return</span> x<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>dequeue方法也主要做了两件事情：</p><ol><li>获取队列中的数据，即获取数组中的数据元素（<code>(E) items[takeIndex]</code>）；</li><li>通知notFull等待队列中的线程，使其由等待队列移入到同步队列中，使其能够有机会获得lock，并执行完成功退出。</li></ol><p>从以上分析，可以看出put和take方法主要是通过condition的通知机制来完成可阻塞式的插入数据和获取数据。在理解ArrayBlockingQueue后再去理解LinkedBlockingQueue就很容易了。</p><h3 id="linkedblockingqueue" tabindex="-1"><a class="header-anchor" href="#linkedblockingqueue" aria-hidden="true">#</a> LinkedBlockingQueue</h3><p>LinkedBlockingQueue是用链表实现的有界阻塞队列，同样满足FIFO的特性，与ArrayBlockingQueue相比起来具有更高的吞吐量，为了防止LinkedBlockingQueue容量迅速增，损耗大量内存。通常在创建LinkedBlockingQueue对象时，会指定其大小，如果未指定，容量等于Integer.MAX_VALUE</p><p>LinkedBlockingQueue的主要属性有：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token doc-comment comment">/** Current number of elements */</span>
<span class="token keyword">private</span> <span class="token keyword">final</span> <span class="token class-name">AtomicInteger</span> count <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">AtomicInteger</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token doc-comment comment">/**
 * Head of linked list.
 * Invariant: head.item == null
 */</span>
<span class="token keyword">transient</span> <span class="token class-name">Node</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">E</span><span class="token punctuation">&gt;</span></span> head<span class="token punctuation">;</span>

<span class="token doc-comment comment">/**
 * Tail of linked list.
 * Invariant: last.next == null
 */</span>
<span class="token keyword">private</span> <span class="token keyword">transient</span> <span class="token class-name">Node</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">E</span><span class="token punctuation">&gt;</span></span> last<span class="token punctuation">;</span>

<span class="token doc-comment comment">/** Lock held by take, poll, etc */</span>
<span class="token keyword">private</span> <span class="token keyword">final</span> <span class="token class-name">ReentrantLock</span> takeLock <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ReentrantLock</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token doc-comment comment">/** Wait queue for waiting takes */</span>
<span class="token keyword">private</span> <span class="token keyword">final</span> <span class="token class-name">Condition</span> notEmpty <span class="token operator">=</span> takeLock<span class="token punctuation">.</span><span class="token function">newCondition</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token doc-comment comment">/** Lock held by put, offer, etc */</span>
<span class="token keyword">private</span> <span class="token keyword">final</span> <span class="token class-name">ReentrantLock</span> putLock <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ReentrantLock</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token doc-comment comment">/** Wait queue for waiting puts */</span>
<span class="token keyword">private</span> <span class="token keyword">final</span> <span class="token class-name">Condition</span> notFull <span class="token operator">=</span> putLock<span class="token punctuation">.</span><span class="token function">newCondition</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>可以看出与ArrayBlockingQueue主要的区别是，LinkedBlockingQueue在插入数据和删除数据时分别是由两个不同的lock（<code>takeLock</code>和<code>putLock</code>）来控制线程安全的，因此，也由这两个lock生成了两个对应的condition（<code>notEmpty</code>和<code>notFull</code>）来实现可阻塞的插入和删除数据。并且，采用了链表的数据结构来实现队列，Node结点的定义为：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">static</span> <span class="token keyword">class</span> <span class="token class-name">Node</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">E</span><span class="token punctuation">&gt;</span></span> <span class="token punctuation">{</span>
    <span class="token class-name">E</span> item<span class="token punctuation">;</span>

    <span class="token doc-comment comment">/**
     * One of:
     * - the real successor Node
     * - this Node, meaning the successor is head.next
     * - null, meaning there is no successor (this is the last node)
     */</span>
    <span class="token class-name">Node</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">E</span><span class="token punctuation">&gt;</span></span> next<span class="token punctuation">;</span>

    <span class="token class-name">Node</span><span class="token punctuation">(</span><span class="token class-name">E</span> x<span class="token punctuation">)</span> <span class="token punctuation">{</span> item <span class="token operator">=</span> x<span class="token punctuation">;</span> <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>接下来，我们也同样来看看put方法和take方法的实现。</p><h4 id="_1-put方法详解-1" tabindex="-1"><a class="header-anchor" href="#_1-put方法详解-1" aria-hidden="true">#</a> 1）put方法详解</h4><p>put方法源码为:</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">put</span><span class="token punctuation">(</span><span class="token class-name">E</span> e<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">InterruptedException</span> <span class="token punctuation">{</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span>e <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token class-name">NullPointerException</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token comment">// Note: convention in all put/take/etc is to preset local var</span>
    <span class="token comment">// holding count negative to indicate failure unless set.</span>
    <span class="token keyword">int</span> c <span class="token operator">=</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">;</span>
    <span class="token class-name">Node</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">E</span><span class="token punctuation">&gt;</span></span> node <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Node</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">E</span><span class="token punctuation">&gt;</span></span><span class="token punctuation">(</span>e<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">final</span> <span class="token class-name">ReentrantLock</span> putLock <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>putLock<span class="token punctuation">;</span>
    <span class="token keyword">final</span> <span class="token class-name">AtomicInteger</span> count <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>count<span class="token punctuation">;</span>
    putLock<span class="token punctuation">.</span><span class="token function">lockInterruptibly</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">try</span> <span class="token punctuation">{</span>
        <span class="token comment">/*
         * Note that count is used in wait guard even though it is
         * not protected by lock. This works because count can
         * only decrease at this point (all other puts are shut
         * out by lock), and we (or some other waiting put) are
         * signalled if it ever changes from capacity. Similarly
         * for all other uses of count in other wait guards.
         */</span>
		<span class="token comment">//如果队列已满，则阻塞当前线程，将其移入等待队列</span>
        <span class="token keyword">while</span> <span class="token punctuation">(</span>count<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">==</span> capacity<span class="token punctuation">)</span> <span class="token punctuation">{</span>
            notFull<span class="token punctuation">.</span><span class="token function">await</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
		<span class="token comment">//入队操作，插入数据</span>
        <span class="token function">enqueue</span><span class="token punctuation">(</span>node<span class="token punctuation">)</span><span class="token punctuation">;</span>
        c <span class="token operator">=</span> count<span class="token punctuation">.</span><span class="token function">getAndIncrement</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
		<span class="token comment">//若队列满足插入数据的条件，则通知被阻塞的生产者线程</span>
        <span class="token keyword">if</span> <span class="token punctuation">(</span>c <span class="token operator">+</span> <span class="token number">1</span> <span class="token operator">&lt;</span> capacity<span class="token punctuation">)</span>
            notFull<span class="token punctuation">.</span><span class="token function">signal</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span> <span class="token keyword">finally</span> <span class="token punctuation">{</span>
        putLock<span class="token punctuation">.</span><span class="token function">unlock</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span>c <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span>
        <span class="token function">signalNotEmpty</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>put方法的逻辑也同样很容易理解，可见注释。基本上和ArrayBlockingQueue的put方法一样。</p><h4 id="_2-take方法" tabindex="-1"><a class="header-anchor" href="#_2-take方法" aria-hidden="true">#</a> 2）take方法</h4><p>源码如下：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">public</span> <span class="token class-name">E</span> <span class="token function">take</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">InterruptedException</span> <span class="token punctuation">{</span>
    <span class="token class-name">E</span> x<span class="token punctuation">;</span>
    <span class="token keyword">int</span> c <span class="token operator">=</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">;</span>
    <span class="token keyword">final</span> <span class="token class-name">AtomicInteger</span> count <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>count<span class="token punctuation">;</span>
    <span class="token keyword">final</span> <span class="token class-name">ReentrantLock</span> takeLock <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>takeLock<span class="token punctuation">;</span>
    takeLock<span class="token punctuation">.</span><span class="token function">lockInterruptibly</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">try</span> <span class="token punctuation">{</span>
		<span class="token comment">//当前队列为空，则阻塞当前线程，将其移入到等待队列中，直至满足条件</span>
        <span class="token keyword">while</span> <span class="token punctuation">(</span>count<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            notEmpty<span class="token punctuation">.</span><span class="token function">await</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
		<span class="token comment">//移除队头元素，获取数据</span>
        x <span class="token operator">=</span> <span class="token function">dequeue</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        c <span class="token operator">=</span> count<span class="token punctuation">.</span><span class="token function">getAndDecrement</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token comment">//如果当前满足移除元素的条件，则通知被阻塞的消费者线程</span>
		<span class="token keyword">if</span> <span class="token punctuation">(</span>c <span class="token operator">&gt;</span> <span class="token number">1</span><span class="token punctuation">)</span>
            notEmpty<span class="token punctuation">.</span><span class="token function">signal</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span> <span class="token keyword">finally</span> <span class="token punctuation">{</span>
        takeLock<span class="token punctuation">.</span><span class="token function">unlock</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span>c <span class="token operator">==</span> capacity<span class="token punctuation">)</span>
        <span class="token function">signalNotFull</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">return</span> x<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
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</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>take方法的主要逻辑请见于注释，也很容易理解。</p><p>** ArrayBlockingQueue与LinkedBlockingQueue的比较**</p><p><strong>相同点</strong>：ArrayBlockingQueue和LinkedBlockingQueue都是通过condition通知机制来实现可阻塞式插入和删除元素，并满足线程安全的特性；</p><p><strong>不同点</strong>：</p><ol><li>ArrayBlockingQueue底层是采用的数组进行实现，而LinkedBlockingQueue则是采用链表数据结构；</li><li>ArrayBlockingQueue插入和删除数据，只采用了一个lock，而LinkedBlockingQueue则是在插入和删除分别采用了<code>putLock</code>和<code>takeLock</code>，这样可以降低线程由于线程无法获取到lock而进入WAITING状态的可能性，从而提高了线程并发执行的效率。</li></ol><h3 id="priorityblockingqueue" tabindex="-1"><a class="header-anchor" href="#priorityblockingqueue" aria-hidden="true">#</a> PriorityBlockingQueue</h3><p>PriorityBlockingQueue是一个支持优先级的无界阻塞队列。默认情况下元素采用自然顺序进行排序，也可以通过自定义类实现compareTo()方法来指定元素排序规则，或者初始化时通过构造器参数Comparator来指定排序规则。</p><h3 id="synchronousqueue" tabindex="-1"><a class="header-anchor" href="#synchronousqueue" aria-hidden="true">#</a> SynchronousQueue</h3><p>SynchronousQueue每个插入操作必须等待另一个线程进行相应的删除操作，因此，SynchronousQueue实际上没有存储任何数据元素，因为只有线程在删除数据时，其他线程才能插入数据，同样的，如果当前有线程在插入数据时，线程才能删除数据。SynchronousQueue也可以通过构造器参数来为其指定公平性。</p><h3 id="linkedtransferqueue" tabindex="-1"><a class="header-anchor" href="#linkedtransferqueue" aria-hidden="true">#</a> LinkedTransferQueue</h3><p>LinkedTransferQueue是一个由链表数据结构构成的无界阻塞队列，由于该队列实现了TransferQueue接口，与其他阻塞队列相比主要有以下不同的方法：</p><p><strong>transfer(E e)</strong> 如果当前有线程（消费者）正在调用take()方法或者可延时的poll()方法进行消费数据时，生产者线程可以调用transfer方法将数据传递给消费者线程。如果当前没有消费者线程的话，生产者线程就会将数据插入到队尾，直到有消费者能够进行消费才能退出；</p><p><strong>tryTransfer(E e)</strong> tryTransfer方法如果当前有消费者线程（调用take方法或者具有超时特性的poll方法）正在消费数据的话，该方法可以将数据立即传送给消费者线程，如果当前没有消费者线程消费数据的话，就立即返回<code>false</code>。因此，与transfer方法相比，transfer方法是必须等到有消费者线程消费数据时，生产者线程才能够返回。而tryTransfer方法能够立即返回结果退出。</p><p><code>tryTransfer(E e,long timeout,imeUnit unit)</code> 与transfer基本功能一样，只是增加了超时特性，如果数据才规定的超时时间内没有消费者进行消费的话，就返回<code>false</code>。</p><h3 id="linkedblockingdeque" tabindex="-1"><a class="header-anchor" href="#linkedblockingdeque" aria-hidden="true">#</a> LinkedBlockingDeque</h3><p>LinkedBlockingDeque是基于链表数据结构的有界阻塞双端队列，如果在创建对象时为指定大小时，其默认大小为Integer.MAX_VALUE。与LinkedBlockingQueue相比，主要的不同点在于，LinkedBlockingDeque具有双端队列的特性。LinkedBlockingDeque基本操作如下图所示（来源于java文档）</p><p><img src="http://cdn.tobebetterjavaer.com/tobebetterjavaer/images/thread/BlockingQueue-02.png" alt=""></p><p>如上图所示，LinkedBlockingDeque的基本操作可以分为四种类型：</p><ol><li>特殊情况，抛出异常；</li><li>特殊情况，返回特殊值如null或者false；</li><li>当线程不满足操作条件时，线程会被阻塞直至条件满足；</li><li>操作具有超时特性。</li></ol><p>另外，LinkedBlockingDeque实现了BlockingDueue接口而LinkedBlockingQueue实现的是BlockingQueue，这两个接口的主要区别如下图所示（来源于java文档）：</p><p><img src="http://cdn.tobebetterjavaer.com/tobebetterjavaer/images/thread/BlockingQueue-03.png" alt="BlockingQueue和BlockingDeque的区别"></p><p>从上图可以看出，两个接口的功能是可以等价使用的，比如BlockingQueue的add方法和BlockingDeque的addLast方法的功能是一样的。</p><h3 id="delayqueue" tabindex="-1"><a class="header-anchor" href="#delayqueue" aria-hidden="true">#</a> DelayQueue</h3><p>DelayQueue是一个存放实现Delayed接口的数据的无界阻塞队列，只有当数据对象的延时时间达到时才能插入到队列进行存储。如果当前所有的数据都还没有达到创建时所指定的延时期，则队列没有队头，并且线程通过poll等方法获取数据元素则返回null。所谓数据延时期满时，则是通过Delayed接口的<code>getDelay(TimeUnit.NANOSECONDS)</code>来进行判定，如果该方法返回的是小于等于0则说明该数据元素的延时期已满。</p><hr><blockquote><p>编辑：沉默王二，内容大部分来源以下三个开源仓库：</p><ul><li><a href="http://concurrent.redspider.group/" target="_blank" rel="noopener noreferrer">深入浅出 Java 多线程<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewbox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a></li><li><a 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