java线程池的使用

public ThreadPoolExecutor(int corePoolSize,
                          int maximumPoolSize,
                          long keepAliveTime,
                          TimeUnit unit,
                          BlockingQueue<Runnable> workQueue) {
    this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
         Executors.defaultThreadFactory(), defaultHandler);
}

package threadpool;

import java.util.List;
import java.util.concurrent.*;

public class ThreadPoolTest {

    public static void main(String[] args) {
        //创建固定大小的线程池
        ExecutorService executorService = Executors.newFixedThreadPool(2);
        //创建只有1个线程的线程池
        ExecutorService executorService1 = Executors.newSingleThreadExecutor();
        //创建一个不限线程上限的线程池，任何提交的任务度可以立刻执行
        ExecutorService executorService2 = Executors.newCachedThreadPool();

        //线程池的工作顺序
        //corepoolsize-》任务队列--》maximumPoolSize->拒绝策略

        //向线程池提交的2种类型的任务 Runnable,Callable
        //1、方法签名不一样 void Runnable.run() V Callable.call() throws Exception
        //2 是否允许有返回值 Callable允许
        //3 是否允许抛一场 Callable允许
        //三种提交任务方式
        Future<?> submit = executorService.submit(new Runnable() {
            @Override
            public void run() {

            }
        });
        Future<String> submit1 = executorService.submit(new Callable<String>() {
            @Override
            public String call() throws Exception {
                return "null";
            }
        });
        //正确使用线程池
        //避免使用无边界队列
        ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(2, 2, 0, TimeUnit.SECONDS, new ArrayBlockingQueue<>(512), new ThreadPoolExecutor.AbortPolicy());

        //线程池的拒绝策略
        //ThreadPoolExecutor.AbortPolicy :抛出异常； ThreadPoolExecutor.DiscardPolicy 什么也不做
        //ThreadPoolExecutor.DiscardOldestPolicy 丢弃执行队列最老的任务，尝试为当前提交的任务腾出空间
        //        ThreadPoolExecutor.CallerRunsPolicy 直接有提交任务这执行这个任务
       // 获取结果以及异常
        try {
            String s = submit1.get();
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } catch (ExecutionException e) {
            throw new RuntimeException(e);
        }

        //正确使用线程池子


    }

    void testLaunch(ExecutorService executorService, List<Runnable> runnableList){
        CountDownLatch countDownLatch=new CountDownLatch(runnableList.size());
        for (Runnable r:runnableList){
            executorService.submit(new Runnable() {
                @Override
                public void run() {
                    try {
                        r.run();
                    }finally {
                        countDownLatch.countDown();
                    }

                }
            });
        }
        countDownLatch.await(10,TimeUnit.SECONDS);
    }
}