MainActivity例如以下:
package cc.vv; import java.util.concurrent.LinkedBlockingQueue; import java.util.concurrent.ThreadPoolExecutor; import java.util.concurrent.TimeUnit; import android.os.Bundle; import android.app.Activity; /** * Demo描写叙述: * 线程池(ThreadPoolExecutor)及其拒绝策略(RejectedExecutionHandler)使用演示样例 * * 工作原理: * 线程池的工作中主要涉及到:corePoolSize,workQueue,maximumPoolSize,RejectedExecutionHandler * 它们的调用原理: * 1 当线程池中线程数量小于corePoolSize则创建线程,并处理请求 * 2 当线程池中线程数量等于corePoolSize则把请求放入workQueue中,线程池中的的空暇线程就从workQueue中取任务并处理 * 3 当workQueue已满存放不下新入的任务时则新建线程入池,并处理请求; * 假设线程池中线程数大于maximumPoolSize则用RejectedExecutionHandler使用一定的策略来做拒绝处理 * * 在该机制中另一个keepAliveTime,文档描写叙述例如以下: * when the number of threads is greater than the core, * this is the maximum time that excess idle threads will wait for new tasks before terminating. * 它是什么意思呢? * 比方线程池中一共同拥有5个线程,当中3个为核心线程(core)其余两个为非核心线程. * 当超过一定时间(keepAliveTime)非核心线程仍然闲置(即没有运行任务或者说没有任务可运行)那么该非核心线程就会被终止. * 即线程池中的非核心且空暇线程所能持续的最长时间,超过该时间后该线程被终止. * * * RejectedExecutionHandler的四种拒绝策略 * * hreadPoolExecutor.AbortPolicy: * 当线程池中的数量等于最大线程数时抛出java.util.concurrent.RejectedExecutionException异常. * 涉及到该异常的任务也不会被运行. * * ThreadPoolExecutor.CallerRunsPolicy(): * 当线程池中的数量等于最大线程数时,重试加入当前的任务;它会自己主动反复调用execute()方法 * * ThreadPoolExecutor.DiscardOldestPolicy(): * 当线程池中的数量等于最大线程数时,抛弃线程池中工作队列头部的任务(即等待时间最久Oldest的任务),并运行新传入的任务 * * ThreadPoolExecutor.DiscardPolicy(): * 当线程池中的数量等于最大线程数时,丢弃不能运行的新加任务 * * 參考资料: * http://blog.csdn.net/cutesource/article/details/6061229 * http://blog.csdn.net/longeremmy/article/details/8231184 * http://blog.163.com/among_1985/blog/static/275005232012618849266/ * http://blog.csdn.net/longeremmy/article/details/8231184 * http://ifeve.com/java-threadpool/ * http://www.blogjava.net/xylz/archive/2010/07/08/325587.html * http://blog.csdn.net/ns_code/article/details/17465497 * Thank you very much * */ public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); testRejectedExecutionHandler(); } // 在此分别測试四种策略,替换ThreadPoolExecutor()方法最后一个參数就可以. private void testRejectedExecutionHandler() { int produceTaskMaxNumber = 10; // 构造一个线程池 ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(2, 4, 3, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>(3), new ThreadPoolExecutor.DiscardPolicy()); for (int i = 1; i <= produceTaskMaxNumber; i++) { try { String task = "任务" + i; System.out.println("将" + task + "放入线程池"); threadPoolExecutor.execute(new RunnableImpl(task)); } catch (Exception e) { e.printStackTrace(); System.out.println("AbortPolicy策略抛出异常----> " + e.toString()); } } } private class RunnableImpl implements Runnable { private String taskName; private int consumerTaskSleepTime = 2000; RunnableImpl(String taskName) { this.taskName = taskName; } public void run() { System.out.println("開始 " + taskName); try { // 模拟耗时任务 Thread.sleep(consumerTaskSleepTime); } catch (Exception e) { e.printStackTrace(); } System.out.println("完毕 " + taskName); } } }
main.xml例如以下:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context=".MainActivity" > <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/hello_world" /> </RelativeLayout>