CompletableFuture-通用异步编程

演示Completable接口完全可以代替Future接口：

CompletableFuture减少阻塞和轮询，可以传入回调对象，当异步任务完成或者发生异常时，自动

调用回调对象的回调方法。

package com.nanjing.gulimall.zhouyimo.test;
 
import java.util.concurrent.*;
 
/**
 * @author zhou
 */
public class CompletableFutureUseDemo {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        ExecutorService executorService = Executors.newFixedThreadPool(3);
        CompletableFuture completableFuture = CompletableFuture.supplyAsync(() -> {
            System.out.println(Thread.currentThread().getName() + "---come in");
            int result = ThreadLocalRandom.current().nextInt(10);
            try {
                TimeUnit.SECONDS.sleep(1);
            } catch (