简单测试线程池拒绝执行任务策略

线程池多余任务的拒绝执行策略有四中，分别是直接丢弃任务DiscardPolicy，
丢弃old线程任务DiscardOldestPolicy，抛出异常AbortPolicy和调用线程执行多余任务CallerRunsPolicy，
下面我们用一个实例来测试一下这几种策略：
测试实例：

package juc.executor;

import java.lang.reflect.Field;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.ThreadPoolExecutor.AbortPolicy;
import java.util.concurrent.TimeUnit;

/**
 * 测试线程池拒绝执行任务策略
 * 
 * @author donald 2017年3月24日 上午8:56:07
 */
public class TestRejectedExecutionHandler {
	/**
	 * 
	 * @param msg
	 */
	static void log(String msg) {
		System.out.println("time："+System.currentTimeMillis() + " -> " + msg);
	}

	public static void main(String[] args) throws Exception {
		ThreadPoolExecutor pool = new ThreadPoolExecutor(1, 1, 0, TimeUnit.SECONDS,
				new ArrayBlockingQueue<Runnable>(1));
		//直接丢弃任务
		 pool.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardPolicy());
		//丢弃old线程任务
//		 pool.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardOldestPolicy());
		//抛出异常
//		 pool.setRejectedExecutionHandler(new ThreadPoolExecutor.AbortPolicy());
		//调用线程执行多余任务
//		pool.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
		for (int i = 0; i < 10; i++) {
			final int index = i;
			pool.submit(new Runnable() {
				public void run() {
					log("run task:" + index + " -> " + Thread.currentThread().getName());
					try {
						Thread.sleep(1000L);
					} catch (Exception e) {
						e.printStackTrace();
					}
					log("run over:" + index + " -> " + Thread.currentThread().getName());
				}
			});
		}
		log("==========before sleep");
		Thread.sleep(4000L);
		log("==========before shutdown()");
		pool.shutdown();
		log("==========after shutdown(),pool.isTerminated=" + pool.isTerminated());
		pool.awaitTermination(1000L, TimeUnit.SECONDS);
		log("==========now,pool.isTerminated=" + pool.isTerminated());
	}	
}

分别使用四中多余任务执行策略，
直接丢弃任务DiscardPolicy：
控制台输出:多余任务直接丢弃
time：1490366101248 -> ==========before sleep
time：1490366101248 -> run task:0 -> pool-1-thread-1
time：1490366102250 -> run over:0 -> pool-1-thread-1
time：1490366102250 -> run task:1 -> pool-1-thread-1
time：1490366103251 -> run over:1 -> pool-1-thread-1
time：1490366105250 -> ==========before shutdown()
time：1490366105251 -> ==========after shutdown(),pool.isTerminated=false
time：1490366105253 -> ==========now,pool.isTerminated=true


丢弃old线程任务DiscardOldestPolicy：
控制台输出:直接丢弃旧的任务
time：1490366209872 -> run task:0 -> pool-1-thread-1
time：1490366209872 -> ==========before sleep
time：1490366210872 -> run over:0 -> pool-1-thread-1
time：1490366210872 -> run task:9 -> pool-1-thread-1
time：1490366211875 -> run over:9 -> pool-1-thread-1
time：1490366213872 -> ==========before shutdown()
time：1490366213873 -> ==========after shutdown(),pool.isTerminated=false
time：1490366213874 -> ==========now,pool.isTerminated=true


抛出异常：AbortPolicy
控制台输出:抛出异常
time：1490366258974 -> run task:0 -> pool-1-thread-1Exception in thread "main"
java.util.concurrent.RejectedExecutionException: Task java.util.concurrent.FutureTask@3639b3a2 rejected from java.util.concurrent.ThreadPoolExecutor@684be8b8[Running, pool size = 1, active threads = 1, queued tasks = 1, completed tasks = 0]
at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2048)
at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:821)
at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1372)
at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:110)
at juc.executor.TestRejectedExecutionHandler.main(TestRejectedExecutionHandler.java:36)
time：1490366259974 -> run over:0 -> pool-1-thread-1
time：1490366259974 -> run task:1 -> pool-1-thread-1
time：1490366260976 -> run over:1 -> pool-1-thread-1

调用线程执行多余任务：CallerRunsPolicy
控制台输出:调用线程执行多余任务
time：1490366322359 -> run task:0 -> pool-1-thread-1
time：1490366322359 -> run task:2 -> main
time：1490366323360 -> run over:0 -> pool-1-thread-1
time：1490366323360 -> run over:2 -> main
time：1490366323360 -> run task:1 -> pool-1-thread-1
time：1490366323360 -> run task:4 -> main
time：1490366324361 -> run over:4 -> main
time：1490366324361 -> run over:1 -> pool-1-thread-1
time：1490366324361 -> run task:5 -> main
time：1490366324361 -> run task:3 -> pool-1-thread-1
time：1490366325362 -> run over:5 -> main
time：1490366325362 -> run task:7 -> main
time：1490366325363 -> run over:3 -> pool-1-thread-1
time：1490366325363 -> run task:6 -> pool-1-thread-1
time：1490366326363 -> run over:7 -> main
time：1490366326363 -> run over:6 -> pool-1-thread-1
time：1490366326363 -> run task:8 -> pool-1-thread-1
time：1490366326363 -> run task:9 -> main
time：1490366327365 -> run over:9 -> main
time：1490366327365 -> run over:8 -> pool-1-thread-1
time：1490366327365 -> ==========before sleep
time：1490366331366 -> ==========before shutdown()
time：1490366331367 -> ==========after shutdown(),pool.isTerminated=false
time：1490366331367 -> ==========now,pool.isTerminated=true