Scheduled线程-schedule

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本文通过三个实验详细介绍了ScheduledThreadPool中schedule、scheduleAtFixedRate和scheduleWithFixedDelay三种方法的区别及应用场景，展示了不同方法如何影响任务的调度与执行。

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schedule

1.schedule方法

schedule方法主要使用延迟或者定时执行一次，在指定时间之后。

在延迟两秒后提交任务，开始任务的执行

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 ScheduledThreadPool {
    private static final Logger LOGGER = LoggerFactory.getLogger(ScheduledThreadPool.class);

    public static void main(String[] args) throws ExecutionException, InterruptedException {
        testScheduledMethod();
        testFixScheduledMethod();
        testFixWithScheduledMethod();
    }

    private static void testScheduledMethod() throws ExecutionException, InterruptedException {
        int poolSize = 2;
        ScheduledExecutorService executorService = Executors.newScheduledThreadPool(poolSize);
        List<Future<CallerHandle>> futureList = new ArrayList<>();
        for (int i = 0; i < poolSize * 2; i++) {
            futureList.add(executorService.schedule(new CallableWorker(), 2, TimeUnit.SECONDS));
        }
        executorService.shutdown();
        LOGGER.info("线程池已经被关闭");
        for (Future<CallerHandle> future : futureList) {
            CallerHandle handle = future.get();
            LOGGER.info(handle.getThreadName() + "已经完成");
        }
        LOGGER.info("主线程结束");
    }

    private static void testFixScheduledMethod() throws ExecutionException, InterruptedException {
        int poolSize = 2;
        ScheduledExecutorService executorService = Executors.newScheduledThreadPool(poolSize);
        for (int i = 0; i < poolSize * 2; i++) {
            executorService.scheduleAtFixedRate(new RunableWorker(), 0, 5, TimeUnit.SECONDS);
        }
        executorService.awaitTermination(10, TimeUnit.SECONDS);
        executorService.shutdown();
        LOGGER.info("线程池已经被关闭");
        LOGGER.info("主线程结束");
    }

    private static void testFixWithScheduledMethod() throws ExecutionException, InterruptedException {
        int poolSize = 2;
        ScheduledExecutorService executorService = Executors.newScheduledThreadPool(poolSize);
        for (int i = 0; i < poolSize * 2; i++) {
            executorService.scheduleWithFixedDelay(new RunableWorker(), 0, 5, TimeUnit.SECONDS);
        }
        executorService.awaitTermination(10, TimeUnit.SECONDS);
        executorService.shutdown();
        LOGGER.info("线程池已经被关闭");
        LOGGER.info("主线程结束");
    }
}

testScheduledMethod结果如下：

22:04:41.017  INFO (ScheduledThreadPool.java:29) - 线程池已经被关闭
22:04:45.023  INFO (CallableWorker.java:20) - pool-1-thread-1 结束任务
22:04:45.024  INFO (CallableWorker.java:20) - pool-1-thread-2 结束任务
22:04:45.026  INFO (ScheduledThreadPool.java:32) - pool-1-thread-1已经完成
22:04:45.027  INFO (ScheduledThreadPool.java:32) - pool-1-thread-2已经完成
22:04:47.029  INFO (CallableWorker.java:20) - pool-1-thread-1 结束任务
22:04:47.029  INFO (CallableWorker.java:20) - pool-1-thread-2 结束任务
22:04:47.029  INFO (ScheduledThreadPool.java:32) - pool-1-thread-1已经完成
22:04:47.030  INFO (ScheduledThreadPool.java:32) - pool-1-thread-2已经完成
22:04:47.030  INFO (ScheduledThreadPool.java:34) - 主线程结束

注意：scheduleAtFixedRate只会同时调度指定线程数量的任务,其他的任务执行时间会延后，但是其调度延迟时间是按照任务执行开始时间进行计算。

testFixScheduledMethod执行结果如下：

22:46:37.313  INFO (RunableWorker.java:27) - pool-1-thread-2 线程处理提交任务完成
22:46:37.313  INFO (RunableWorker.java:27) - pool-1-thread-1 线程处理提交任务完成
22:46:39.318  INFO (RunableWorker.java:27) - pool-1-thread-2 线程处理提交任务完成
22:46:39.324  INFO (RunableWorker.java:27) - pool-1-thread-1 线程处理提交任务完成
22:46:42.316  INFO (RunableWorker.java:27) - pool-1-thread-2 线程处理提交任务完成
22:46:42.316  INFO (RunableWorker.java:27) - pool-1-thread-1 线程处理提交任务完成
22:46:44.321  INFO (RunableWorker.java:27) - pool-1-thread-1 线程处理提交任务完成
22:46:44.321  INFO (RunableWorker.java:27) - pool-1-thread-2 线程处理提交任务完成
22:46:45.311  INFO (ScheduledThreadPool.java:47) - 线程池已经被关闭
22:46:45.312  INFO (ScheduledThreadPool.java:48) - 主线程结束
22:46:47.314  INFO (RunableWorker.java:27) - pool-1-thread-1 线程处理提交任务完成

注意：scheduleWithFixedDelay只会同时调度指定线程数量的任务,其他的任务执行时间会延后，但是其调度延迟时间是按照任务结束时间进行计算。

testFixWithScheduledMethod执行如下：

22:49:50.897  INFO (RunableWorker.java:27) - pool-1-thread-1 线程处理提交任务完成
22:49:50.897  INFO (RunableWorker.java:27) - pool-1-thread-2 线程处理提交任务完成
22:49:52.906  INFO (RunableWorker.java:27) - pool-1-thread-1 线程处理提交任务完成
22:49:52.906  INFO (RunableWorker.java:27) - pool-1-thread-2 线程处理提交任务完成
22:49:57.907  INFO (RunableWorker.java:27) - pool-1-thread-1 线程处理提交任务完成
22:49:57.907  INFO (RunableWorker.java:27) - pool-1-thread-2 线程处理提交任务完成
22:49:58.895  INFO (ScheduledThreadPool.java:59) - 线程池已经被关闭
22:49:58.896  INFO (ScheduledThreadPool.java:60) - 主线程结束
22:49:59.911  INFO (RunableWorker.java:27) - pool-1-thread-2 线程处理提交任务完成
22:49:59.911  INFO (RunableWorker.java:27) - pool-1-thread-1 线程处理提交任务完成