vertx future 
java.util.concurrent  CompletionStage
CompletionStage 接口代表异步操作中的一个步骤，可以将其视为future
CompletionStage< Void> thenRunAsync(Runnable,Executor)， 没有执行器参数的变体默认分派到 ForkJoinPool 实例



import dyyx.util.CommUtil;
import io.vertx.core.Future;
import io.vertx.core.Promise;
import io.vertx.core.Vertx;

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

public class FutureAndCompleteStageDemo {
    static Promise< String> promise = Promise.promise();
    // static Vertx vertx = Vertx.vertx();

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

        Task task = new Task();
        // 启动线程  sleep 1s 后 ，设置 promise 返回值 ，成功或失败
        task.start();
        System.out.println(LocalDateTime.now());

        //  从 Vert.x Future 到 CompletionStage
        CompletionStage cs = promise.future().toCompletionStage();
        cs.thenApply(String::toUpperCase)
                .thenApply(str -> "~~~ " + str)
                .whenComplete((str, err) -> {
                    if (err == null) {
                        System.out.println("ok,"+str);
                    } else {
                        System.out.println("error," + err);
                    }
                });

        // 从 CompletionStage 到 Vert.x Future
        CompletableFuture cf2 = CompletableFuture.supplyAsync(() -> {
            try {
                System.out.println(LocalDateTime.now()+","+Thread.currentThread());
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return "2 seconds have elapsed";
        });

        Future.fromCompletionStage(cf2)
                .onSuccess(System.out::println)
                .onFailure(Throwable::printStackTrace);

        Thread.sleep(10*1000);

    }

    private static class Task extends Thread{

        public void run(){
            // sleep 1 s
            CommUtil.doSleep(1000);
            // 设置返回结果
            promise.complete("hello");
            // 设置异常
            // promise.fail(new Throwable("error"));
        }

    }
}