线程池-callable任务

约定不等于承诺〃 2022-07-16 11:07 248阅读 0赞

## 1 带回调的线程池任务 ##

Callable接口和Runable接口最大的区别是Callable可以拥有返回值，并可以通过回调的方式获取。同时通过Future的get方法，可以同步的获取到返回值，并保证任务已经完成

package com.cweeyii.threadpool;
    
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    
    import java.util.ArrayList;
    import java.util.List;
    import java.util.concurrent.*;
    
    /** * Created by wenyi on 16/10/16. * Email:caowenyi@meituan.com */
    public class CallableThreadPool { 
        private static final Logger LOGGER = LoggerFactory.getLogger(CallableThreadPool.class);
    
        public static void main(String[] args) throws InterruptedException, ExecutionException {
            int threadSize = 2;
            ExecutorService executorService = Executors.newFixedThreadPool(threadSize);
            List<Future<CallerHandle>> futureList=new ArrayList<>();
            for (int i = 0; i < threadSize * 2; i++) {
                CallableWorker worker = new CallableWorker();
                Future<CallerHandle> future = executorService.submit(worker);
                futureList.add(future);
            }
            executorService.shutdown();
            for(Future<CallerHandle> future:futureList){
                CallerHandle callerHandle=future.get();
                LOGGER.info("{} 已经完成任务",callerHandle.getThreadName());
            }
            LOGGER.info("线程池关闭成功");
        }
    }

14:26:37.574  INFO (CallableWorker.java:20) - pool-1-thread-1 结束任务
    14:26:37.575  INFO (CallableWorker.java:20) - pool-1-thread-2 结束任务
    14:26:37.579  INFO (CallableThreadPool.java:29) - pool-1-thread-1 已经完成任务
    14:26:37.582  INFO (CallableThreadPool.java:29) - pool-1-thread-2 已经完成任务
    14:26:39.583  INFO (CallableWorker.java:20) - pool-1-thread-1 结束任务
    14:26:39.583  INFO (CallableWorker.java:20) - pool-1-thread-2 结束任务
    14:26:39.583  INFO (CallableThreadPool.java:29) - pool-1-thread-1 已经完成任务
    14:26:39.584  INFO (CallableThreadPool.java:29) - pool-1-thread-2 已经完成任务
    14:26:39.584  INFO (CallableThreadPool.java:32) - 线程池关闭成功

ps：注意必须调用线程池的shutdown方法，否则JVM虚拟机不会结束。同理子线程如果为非守护线程，JVM也必须等待所有线程结束后才能结束。

示例1：菲守护线程

package com.cweeyii.threadpool;
    
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    
    /** * Created by wenyi on 16/10/16. * Email:caowenyi@meituan.com */
    public class MainExit { 
        private static final Logger LOGGER = LoggerFactory.getLogger(MainExit.class);
    
        public static void main(String[] args) {
            new Thread(new SleepWorker()).start();
            new Thread(new SleepWorker()).start();
            LOGGER.info("主线程main已经完成={}",Thread.currentThread().getName());
        }
    }

15:57:06.639  INFO (MainExit.java:16) - 主线程main已经完成=main
    15:57:08.641  INFO (SleepWorker.java:31) - threadName=Thread-1 线程结束null工作
    15:57:08.641  INFO (SleepWorker.java:31) - threadName=Thread-0 线程结束null工作

示例2：守护线程

public class MainExit {
        private static final Logger LOGGER = LoggerFactory.getLogger(MainExit.class);
    
        public static void main(String[] args) {
            Thread thread1=new Thread(new SleepWorker());
            Thread thread2=new Thread(new SleepWorker());
            thread1.setDaemon(true);
            thread2.setDaemon(true);
            LOGGER.info("主线程main已经完成={}",Thread.currentThread().getName());
        }
    }

15:58:00.128 INFO (MainExit.java:18) - 主线程main已经完成=main