使用CompletionService解决耗时时间过长任务导致的阻塞问题以及解决ExecutorService.shutdownNow()导致正在执行中的任务被打断，但该任务不会被返回

使用CompletionService解决耗时时间过长任务导致的阻塞问题

package com.dwz.executors;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.CompletionService;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorCompletionService;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
/**
 *    有5个任务，其中4个任务执行速度很快，另1个耗时过长，我们不想等待耗时过长的任务执行完成而想立刻拿到4个执行时间较短任务的结果
 */
public class ComplexExample {
    
    private static Runnable toTask(int i) {
        return () -> {
            try {
                System.out.printf("The task [%d] will be executed.\n", i);
                TimeUnit.SECONDS.sleep(i*5 + 10);
                System.out.printf("The task [%d] executed done.\n", i);
            } catch (InterruptedException e) {
                System.out.printf("The task [%d] be interrupted.\n", i);
            }
        };
    }
    
    private static void test1() throws InterruptedException, ExecutionException {
        final ExecutorService service = Executors.newFixedThreadPool(5);
        List<Runnable> tasks = IntStream.range(0, 5).boxed().map(ComplexExample::toTask).collect(Collectors.toList());
        
        List<Future<?>> futureList = new ArrayList<>();
        tasks.forEach(r -> {
            futureList.add(service.submit(r));
        });
        
        futureList.get(4).get();
        System.out.println("==========4=========");
        futureList.get(3).get();
        System.out.println("==========3=========");
        futureList.get(2).get();
        System.out.println("==========2=========");
        futureList.get(1).get();
        System.out.println("==========1=========");
        futureList.get(0).get();
        System.out.println("==========0=========");
    }
    
    private static void test2() throws InterruptedException, ExecutionException {
        final ExecutorService service = Executors.newFixedThreadPool(5);
        List<Runnable> tasks = IntStream.range(0, 5).boxed().map(ComplexExample::toTask).collect(Collectors.toList());
        
        final CompletionService<Object> completionService = new ExecutorCompletionService<>(service);
        
        tasks.forEach(r -> {
            completionService.submit(Executors.callable(r));
        });
        
        Future<?> future;
        while((future = completionService.take()) != null) {
            System.out.println(future.get());
        }
    }
}

解决ExecutorService.shutdownNow()导致正在执行中的任务被打断，但该任务不会被返回问题

package com.dwz.executors;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.CompletionService;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorCompletionService;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
/**
 *    有5个任务，其中4个任务执行速度很快，另1个耗时过长，我们不想等待耗时过长的任务执行完成而想立刻拿到4个执行时间较短任务的结果
 */
public class ComplexExample {
    //出现执行shutdownNow()之后正在执行中的任务被打断，但该任务不会被返回
    private static void test3() throws InterruptedException, ExecutionException {
        final ExecutorService service = Executors.newSingleThreadExecutor();
        List<Runnable> tasks = IntStream.range(0, 5).boxed().map(ComplexExample::toTask).collect(Collectors.toList());
        
        final CompletionService<Object> completionService = new ExecutorCompletionService<>(service);
        
        tasks.forEach(r -> {
            completionService.submit(Executors.callable(r));
        });
            
        TimeUnit.SECONDS.sleep(12);
        List<Runnable> runnables = service.shutdownNow();
        System.out.println(runnables);
    }
    
    
    private static class MyTask implements Callable<Integer> {
        private final Integer value;
        
        private boolean success = false;
        
        MyTask(Integer value) {
            this.value = value;
        }
        
        public boolean isSuccess() {
            return success;
        }
        
        @Override
        public Integer call() throws Exception {
            System.out.printf("The task [%d] will be executed.\n", this.value);
            TimeUnit.SECONDS.sleep(this.value * 5 + 10);
            System.out.printf("The task [%d] executed done.\n", this.value);
            success = true;
            return this.value;
        }
        
    }
    
    //解决执行shutdownNow()之后正在执行中的任务被打断，让该任务被返回
    private static void test4() throws InterruptedException, ExecutionException {
        final ExecutorService service = Executors.newSingleThreadExecutor();
        List<Callable<Integer>> tasks = IntStream.range(0, 5).boxed().map(MyTask::new).collect(Collectors.toList());
        final CompletionService<Integer> completionService = new ExecutorCompletionService<>(service);
        tasks.forEach(completionService::submit);
        
        TimeUnit.SECONDS.sleep(12);
        service.shutdownNow();
        
        tasks.stream().filter(callable -> !((MyTask) callable).isSuccess()).forEach(System.out::println);
    }
}