ThreadPoolExecutor小记

本文主要是介绍ThreadPoolExecutor小记，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

阿里要求在创建线程池时 不能使用 Excutors，而要使用ThreadPoolExecutor，具体描述如下：

故研究了一下ThreadPoolExecutor，得出的一点小结论记录如下：

ThreadPoolExecutor的构造方法：

public ThreadPoolExecutor(int corePoolSize,int maximumPoolSize,long keepAliveTime,TimeUnit unit,BlockingQueue<Runnable> workQueue) {}

当提交的线程小于corePoolSize时，创建新线程来启动
如果提交线程数大于corePoolSize时，将线程加入workQueue中，如果workQueue满了，则继续创建新线程直到线程数等于maximumPoolSize，此时再提交新的线程，则抛出java.util.concurrent.RejectedExecutionException异常

例

ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(corePoolSize,maximumPoolSize, 0L, TimeUnit.SECONDS, new MyBlockingQueue(queueSize));

上述代码中maximumPoolSize>=corePoolSize,否则会抛出java.lang.IllegalArgumentException异常

• 若提交n个线程（0<=n<=corePoolSize），则线程池创建n个线程并执行
• 若提交n（corePoolSize < n<=corePoolSize+queueSize），则前corePoolSize个提交的线程直接被创建运行，( n-corePoolSize )个线程加入workQueue中等待执行
• 若提交n（corePoolSize+queueSize < n<=maximumPoolSize+queueSize , corePoolSize < maximumPoolSize）则前corePoolSize个提交的线程直接被创建运行，( n-corePoolSize
  )个线程加入workQueue中等待执行，（n-corePoolSize-queueSize）再创建新的线程来执行

测试代码

import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;/*** @author ElinZhou* @version $Id: ThreadPoolTest.java , v 0.1 2017/1/10 10:33 ElinZhou Exp $*/
public class ThreadPoolTest {public static void main(String... args) throws Exception {ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(5, 6, 0L,TimeUnit.SECONDS, new MyBlockingQueue(1));int nThread = 8;for (int i = 0; i < nThread; i++) {System.out.println("create thread " + i);Thread thread = new Thread(new MyRunnable(i));threadPoolExecutor.submit(thread);}//        TimeUnit.SECONDS.sleep(5);}}class MyBlockingQueue extends LinkedBlockingQueue<Runnable> {public MyBlockingQueue() {super();}public MyBlockingQueue(int nThread) {super(nThread);}@Overridepublic boolean offer(Runnable runnable) {System.out.println("invoke offer method:" + runnable);return super.offer(runnable);}
}class MyRunnable implements Runnable {private int id;public MyRunnable(int id) {this.id = id;}@Overridepublic void run() {System.out.println(id + " start at:" + System.currentTimeMillis());try {Thread.sleep(500);} catch (InterruptedException e) {System.out.println(id + " interrupted at:" + System.currentTimeMillis());}System.out.println("------" + id + " end at:" + System.currentTimeMillis());}@Overridepublic String toString() {return "MyRunnable-" + id;}
}

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