JAVA多线程—CompletionService的使用介绍

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CompletionService用于提交一组Callable任务，其take方法返回已完成的一个Callable任务对应的Future对象。

好比我同时种了几块地的麦子，然后就等待收割。收割时，则是那块先成熟了，则先去收割哪块麦子。

示例代码：

package syn;import java.util.concurrent.Callable;import java.util.concurrent.CompletionService;import java.util.concurrent.ExecutorCompletionService;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.Future;public class FutureTest {    public static void main(String[] args) throws Exception {        ExecutorService service = Executors.newFixedThreadPool(3);        CompletionService<Integer> completionService = new ExecutorCompletionService<Integer>(service);        for (int i = 0; i < 10; i++) {            final Integer seq = i + 1;            completionService.submit(new Callable<Integer>() {                public Integer call() throws Exception {                    Thread.sleep((long) (Math.random() * 1000));                    return seq;                }            });        }        for (int i = 0; i < 10; i++) {            Future<Integer> f = completionService.take();            System.out.println(f.get());        }        service.shutdown();    }}

运行结果：
这里写图片描述

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