手写一个简单的线程池

<section id="nice" data-tool="mdnice编辑器" data-website="https://www.mdnice.com" style="line-height: 1.6; word-break: break-word; word-wrap: break-word; text-align: left; font-family: Optima-Regular, Optima, PingFangSC-light, PingFangTC-light, 'PingFang SC', Cambria, Cochin, Georgia, Times, 'Times New Roman', serif; padding: 5px; font-size: 16px; color: #353535; word-spacing: 0.8px; letter-spacing: 0.8px; border-radius: 16px;">  有些人可能对线程池比较陌生，并且更不熟悉线程池的工作原理。所以他们在使用线程的时候，多数情况下都是new Thread来实现多线程。但是，往往良好的多线程设计大多都是使用线程池来实现的。 <h2 data-tool="mdnice编辑器" style="margin-top: 30px; margin-bottom: 15px; padding: 0px; font-weight: bold; color: black; font-size: 22px; text-align: left; margin: 20px 10px 0px 0px;">为什么要使用线程池</h2> <blockquote class="multiquote-2" data-tool="mdnice编辑器" style="border: none; box-shadow: 1px 1px 10px rgba(0,0,0,0.2); padding: 20px; margin-bottom: 20px; margin-top: 20px;"> <blockquote style="border: none;"> <ol style="margin-top: 8px; margin-bottom: 8px; padding-left: 25px; list-style-type: decimal; color: #f83929; font-size: 16px;"> <li><section style="margin-top: 5px; margin-bottom: 5px; line-height: 26px; text-align: left; font-weight: 500; color: #353535;">可以降低线程创建和销毁的资源消耗。</section></li><li><section style="margin-top: 5px; margin-bottom: 5px; line-height: 26px; text-align: left; font-weight: 500; color: #353535;">可以提高响应速度。线程的创建时间为T1，执行时间T2，销毁时间T3，通过使用线程池，可以免去T1和T3的时间</section></li><li><section style="margin-top: 5px; margin-bottom: 5px; line-height: 26px; text-align: left; font-weight: 500; color: #353535;">可以提高线程的可管理性</section></li></ol> </blockquote> </blockquote> 下图所示为线程池的实现原理：    调用方不断向线程池中提交任务，线程池中的线程不断地从队列中取任务，这是一个典型的生产者-消费者模型。

<h2 data-tool="mdnice编辑器" style="margin-top: 30px; margin-bottom: 15px; padding: 0px; font-weight: bold; color: black; font-size: 22px; text-align: left; margin: 20px 10px 0px 0px;">实战：手写简易线程池</h2>   现在来带大家手写一个简单的线程池，让大家更加理解线程池的工作原理 <pre class="custom" data-tool="mdnice编辑器" style="margin-top: 10px; margin-bottom: 10px; border-radius: 5px; box-shadow: rgba(0, 0, 0, 0.55) 0px 2px 10px;"><span style="display: block; background: url(https://files.mdnice.com/user/3441/876cad08-0422-409d-bb5a-08afec5da8ee.svg); height: 30px; width: 100%; background-size: 40px; background-repeat: no-repeat; background-color: #282c34; margin-bottom: -7px; border-radius: 5px; background-position: 10px 10px;"><code class="hljs" style="overflow-x: auto; padding: 16px; color: #abb2bf; display: -webkit-box; font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; font-size: 12px; -webkit-overflow-scrolling: touch; padding-top: 15px; background: #282c34; border-radius: 5px;">/**  * 自定义线程池  */ public class ThreadPool {     /** 默认线程池中的线程的数量 */     private static final int WORK_NUM = 5;     /** 默认处理任务的数量 */     private static final int TASK_NUM = 100;     /** 存放任务 */     private final BlockingQueue<Runnable> taskQueue;     private final Set<WorkThread> workThreads;//保存线程的集合     private int workNumber;//线程数量     private int taskNumber;//任务数量     public ThreadPool(){         this(WORK_NUM , TASK_NUM);     }     public ThreadPool(int workNumber , int taskNumber) {         if (taskNumber<=0){             taskNumber = TASK_NUM;         }         if (workNumber<=0){             workNumber = WORK_NUM;         }         this.taskQueue = new ArrayBlockingQueue<Runnable>(taskNumber);         this.workNumber = workNumber;         this.taskNumber = taskNumber;         workThreads = new HashSet<>();         //工作线程准备好了         //启动一定数量的线程数，从队列中获取任务处理         for (int i=0;i<workNumber;i++) {             WorkThread workThread = new WorkThread("thead_"+i);             workThread.start();             workThreads.add(workThread);         }     }     /**      * 线程池执行任务的方法，其实就是往BlockingQueue中添加元素      * @param task      */     public void execute(Runnable task) {         try {             taskQueue.put(task);         } catch (InterruptedException e) {             // TODO Auto-generated catch block             e.printStackTrace();         }     }     /**      * 销毁线程池      */     public void destroy(){         System.out.println("ready close pool...");         for (WorkThread workThread : workThreads) {             workThread.stopWorker();             workThread = null;//help gc         }         workThreads.clear();     }     /** 内部类，工作线程的实现 */     private class WorkThread extends Thread{         public WorkThread(String name){             super();             setName(name);         }         @Override         public void run() {             while (!interrupted()) {                 try {                     Runnable runnable = taskQueue.take();//获取任务                     if (runnable !=null) {                         System.out.println(getName()+" ready execute:"+runnable.toString());                         runnable.run();//执行任务                     }                     runnable = null;//help gc                 } catch (Exception e) {                     interrupt();                     e.printStackTrace();                 }             }         }         public void stopWorker(){             interrupt();         }     } } </code></pre>   上面代码定义了默认的线程数量和默认处理任务数量，同时用户也可以自定义线程数量和处理任务数量。   我们使用<code style="font-size: 14px; word-wrap: break-word; padding: 2px 4px; border-radius: 4px; margin: 0 2px; background-color: rgba(27,31,35,.05); font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; word-break: break-all; color: rgb(271, 93, 108);">BlockingQueue</code>阻塞队列(之后会具体介绍)来存放任务。用<code style="font-size: 14px; word-wrap: break-word; padding: 2px 4px; border-radius: 4px; margin: 0 2px; background-color: rgba(27,31,35,.05); font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; word-break: break-all; color: rgb(271, 93, 108);">set</code>来存放工作线程；    构造方法中new对象的时候，循环启动线程，并把线程放入<code style="font-size: 14px; word-wrap: break-word; padding: 2px 4px; border-radius: 4px; margin: 0 2px; background-color: rgba(27,31,35,.05); font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; word-break: break-all; color: rgb(271, 93, 108);">set</code>中。    通过实现实现<code style="font-size: 14px; word-wrap: break-word; padding: 2px 4px; border-radius: 4px; margin: 0 2px; background-color: rgba(27,31,35,.05); font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; word-break: break-all; color: rgb(271, 93, 108);">Thread</code>来创建<code style="font-size: 14px; word-wrap: break-word; padding: 2px 4px; border-radius: 4px; margin: 0 2px; background-color: rgba(27,31,35,.05); font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; word-break: break-all; color: rgb(271, 93, 108);">WorkThread</code>类；因为有一个<code style="font-size: 14px; word-wrap: break-word; padding: 2px 4px; border-radius: 4px; margin: 0 2px; background-color: rgba(27,31,35,.05); font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; word-break: break-all; color: rgb(271, 93, 108);">stop</code>方法，所以这里需要<code style="font-size: 14px; word-wrap: break-word; padding: 2px 4px; border-radius: 4px; margin: 0 2px; background-color: rgba(27,31,35,.05); font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; word-break: break-all; color: rgb(271, 93, 108);">while</code>判断，之后从<code style="font-size: 14px; word-wrap: break-word; padding: 2px 4px; border-radius: 4px; margin: 0 2px; background-color: rgba(27,31,35,.05); font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; word-break: break-all; color: rgb(271, 93, 108);">taskQueue</code>队列中获取任务。获取不到就阻塞，获取到的话<code style="font-size: 14px; word-wrap: break-word; padding: 2px 4px; border-radius: 4px; margin: 0 2px; background-color: rgba(27,31,35,.05); font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; word-break: break-all; color: rgb(271, 93, 108);">runnable.run();</code>就执行任务，之后把任务变成null；销毁线程只需要遍历<code style="font-size: 14px; word-wrap: break-word; padding: 2px 4px; border-radius: 4px; margin: 0 2px; background-color: rgba(27,31,35,.05); font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; word-break: break-all; color: rgb(271, 93, 108);">set</code>，把每个线程停止，并且变为<code style="font-size: 14px; word-wrap: break-word; padding: 2px 4px; border-radius: 4px; margin: 0 2px; background-color: rgba(27,31,35,.05); font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; word-break: break-all; color: rgb(271, 93, 108);">null</code>；执行线程任务<code style="font-size: 14px; word-wrap: break-word; padding: 2px 4px; border-radius: 4px; margin: 0 2px; background-color: rgba(27,31,35,.05); font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; word-break: break-all; color: rgb(271, 93, 108);">execute</code>。 我们来测试一下： <pre class="custom" data-tool="mdnice编辑器" style="margin-top: 10px; margin-bottom: 10px; border-radius: 5px; box-shadow: rgba(0, 0, 0, 0.55) 0px 2px 10px;"><span style="display: block; background: url(https://files.mdnice.com/user/3441/876cad08-0422-409d-bb5a-08afec5da8ee.svg); height: 30px; width: 100%; background-size: 40px; background-repeat: no-repeat; background-color: #282c34; margin-bottom: -7px; border-radius: 5px; background-position: 10px 10px;"><code class="hljs" style="overflow-x: auto; padding: 16px; color: #abb2bf; display: -webkit-box; font-family: Operator Mono, Consolas, Monaco, Menlo, monospace; font-size: 12px; -webkit-overflow-scrolling: touch; padding-top: 15px; background: #282c34; border-radius: 5px;">public class TestMySelfThreadPool {     private static final int TASK_NUM = 50;//任务的个数     public static void main(String[] args) {         ThreadPool myPool = new ThreadPool(3,50);         for (int i=0;i<TASK_NUM;i++) {             myPool.execute(new MyTask("task_"+i));         }     }     static class MyTask implements Runnable{         private String name;         public MyTask(String name) {             this.name = name;         }         public String getName() {             return name;         }         public void setName(String name) {             this.name = name;         }         @Override         public void run() {             try {                 Thread.sleep(1000);             } catch (InterruptedException e) {                 // TODO Auto-generated catch block                 e.printStackTrace();             }             System.out.println("task :"+name+" end...");         }         @Override         public String toString() {             // TODO Auto-generated method stub             return "name = "+name;         }     } } </code></pre> 结果ok，没什么问题。 </section>

手写一个简单的线程池

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