CompletableFuture 对 Future 的扩展 ，增加写入机制
Future 只能 调用get 同步阻塞 获取结果

static CompletableFuture< String> future = new CompletableFuture<>();
// 设置返回结果
future.complete(LocalDateTime.now().toString());
// 设置异常
future.completeExceptionally(new Throwable("error"));



import dyyx.util.CommUtil;

import java.time.LocalDateTime;
import java.util.concurrent.CompletableFuture;

public class CompletableFutureDemo {
    static CompletableFuture< String> future = new CompletableFuture<>();

    public static void main(String[]args)throws Exception {

        Task task = new Task();
        task.start();
        System.out.println(LocalDateTime.now());
        // 阻塞 获取结果
        String str = future.get();
        System.out.println(str);

    }

    private static class Task extends Thread{

        public void run(){
            // sleep 1 s
            CommUtil.doSleep(1000);
            // 设置返回结果
            future.complete(LocalDateTime.now().toString());
            // 设置异常
            // future.completeExceptionally(new Throwable("error"));
        }

    }


}


 CompletableFuture 实例