threadPoolExecutor的参数和拒绝策略

package com.example.demo;

import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class ThreadpoolExecutorTest {

    /**
     * 5+2 没用到maximunpoolsize 用到了corePoolSize
     * 8+2 没用到了corePoolSize  用到了maximunpoolsize
     * 大于10 报错 ,这个错看拒绝策略
     * @param args
     */
    public static void main(String[] args) {
        // 创建线程池 ， 参数含义 ：（核心线程数，最大线程数，加开线程的存活时间，时间单位，任务队列长度）
        ThreadPoolExecutor pool = new ThreadPoolExecutor(5, 8,
                0L, TimeUnit.MILLISECONDS,
                new LinkedBlockingQueue<Runnable>(2));
        pool.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardOldestPolicy());

        //设置：任务数 = 3 ～ 11 ,分析：任务数 与 活跃线程数,核心线程数,队列长度,最大线程数的关系。

        int a = 11;

        for (int i = 1; i <= a; i++) {
            int j = i;
            pool.submit(new Runnable() {
                @Override
                public void run() {
                    //获取线程名称
                    Thread thread = Thread.currentThread();
                    String name = thread.getName();
                    //输出
                    int activeCount = pool.getActiveCount();
                    System.out.println("任务：" + j + "-----,线程名称:" + name + "-----活跃线程数:" + activeCount);
                }
            });
        }

        //关闭线程池
        pool.shutdown();

    }
}

　//将被拒绝的任务放到当前调用线程池的线程中去执行
 public static class CallerRunsPolicy implements RejectedExecutionHandler {
        /**
         * Creates a {@code CallerRunsPolicy}.
         */
        public CallerRunsPolicy() { }

        /**
         * Executes task r in the caller's thread, unless the executor
         * has been shut down, in which case the task is discarded.
         *
         * @param r the runnable task requested to be executed
         * @param e the executor attempting to execute this task
         */
        public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
            if (!e.isShutdown()) {
                r.run();
            }
        }
    }

 
//直接丢弃被拒绝的线程池
public static class DiscardPolicy implements RejectedExecutionHandler {
        /**
         * Creates a {@code DiscardPolicy}.
         */
        public DiscardPolicy() { }

        /**
         * Does nothing, which has the effect of discarding task r.
         *
         * @param r the runnable task requested to be executed
         * @param e the executor attempting to execute this task
         */
        public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
        }
    }

//丢弃嘴后面的线程给新来的线程让位置 
 public static class DiscardOldestPolicy implements RejectedExecutionHandler {
        /**
         * Creates a {@code DiscardOldestPolicy} for the given executor.
         */
        public DiscardOldestPolicy() { }

        /**
         * Obtains and ignores the next task that the executor
         * would otherwise execute, if one is immediately available,
         * and then retries execution of task r, unless the executor
         * is shut down, in which case task r is instead discarded.
         *
         * @param r the runnable task requested to be executed
         * @param e the executor attempting to execute this task
         */
        public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
            if (!e.isShutdown()) {
                e.getQueue().poll();
                e.execute(r);
            }
        }
    }

 
//默认的拒绝策略，报错，抛弃任务
public static class AbortPolicy implements RejectedExecutionHandler {
        /**
         * Creates an {@code AbortPolicy}.
         */
        public AbortPolicy() { }

        /**
         * Always throws RejectedExecutionException.
         *
         * @param r the runnable task requested to be executed
         * @param e the executor attempting to execute this task
         * @throws RejectedExecutionException always
         */
        public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
            throw new RejectedExecutionException("Task " + r.toString() +
                                                 " rejected from " +
                                                 e.toString());
        }
    }