Java线程池ThreadPoolExecutor的四种拒绝策略

package thread;

import java.util.concurrent.*;
import java.util.stream.IntStream;

public class ThreadPoolExecutorDemo {
    public static void main(String[] args) {
        int corePoolSize = 10;
        int maxPoolSize = 10;
        long keepAliveTime = 1000;
        TimeUnit timeUnit = TimeUnit.MILLISECONDS;
        BlockingQueue<Runnable> workQueue = new ArrayBlockingQueue<Runnable>(1000);

        // 队列满之后，则丢弃队列中的旧任务
        // RejectedExecutionHandler handler = new ThreadPoolExecutor.DiscardOldestPolicy();

        // 队列满之后，则丢弃新的任务
        // RejectedExecutionHandler handler = new ThreadPoolExecutor.DiscardPolicy();

        // 队列满之后，会将任务分配给调用者线程。所有任务都会得到执行
        // RejectedExecutionHandler handler = new ThreadPoolExecutor.CallerRunsPolicy();

        // 队列满之后，程序进入阻塞。是ThreadPoolExecutor的默认拒绝策略
        RejectedExecutionHandler handler = new ThreadPoolExecutor.AbortPolicy();

        ExecutorService es = new ThreadPoolExecutor(corePoolSize, maxPoolSize, keepAliveTime, timeUnit, workQueue, handler);
        IntStream.range(1, 10000).forEach(i -> es.submit(new MyTask("TaskOne_" + i)));
        es.shutdown();
    }
}

自定义拒绝策略，新建线程来处理无法加入队列的任务。是Netty使用的拒绝策略。

package thread;

import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.ThreadPoolExecutor;

public class NewThreadRunsPolicy implements RejectedExecutionHandler {
    public NewThreadRunsPolicy() {
        super();
    }

    @Override
    public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
        try {
            Thread t = new Thread(r, "Temporary task executor");
            t.start();
        } catch (Throwable t) {
            throw new RejectedExecutionException("Failed to start a new thread", t);
        }
    }
}

相关资料：java线程池ThreadPoolExecutor八种拒绝策略浅析_chihujiang3132的博客-优快云博客z