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

complete 方法传入结果 触发回调

Future代表一个只读的结果的容器 , Promise是一次性可写的,并且实现了Future的接口。
Java 1.8 版本引入了 CompletableFuture ，
CompletableFuture 实现的 CompletionStage 接口定义了一系列的流畅的编程接口以支持灵活扩展异步计算。
CompletableFuture 支持写入结果，实现了 Promise 的写入语义。
CompletableFuture = Future + Promise

 vertx promise future   





package dyyx.conc;

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

public class CompletableFutureDemo {

	public static void main(String[] args) throws Exception {
		CompletableFuture<String> f = new CompletableFuture<>();

		CompletableFuture<String> f2 = f.whenComplete((result, error) -> {
			System.out.println("result=" + result + ",error=" + error + "," + LocalDateTime.now());
		});
		System.out.println("f=" + f + "," + LocalDateTime.now());

		System.out.println("f2=" + f2 + "," + LocalDateTime.now());
		Thread.sleep(1000);
		//
		f.complete("hello");

		System.out.println("f=" + f);
		System.out.println("f2=" + f2);

		System.out.println("f.result=" + f.get());
		System.out.println("f2.result=" + f2.get());

		Thread.sleep(1000);
		
		CompletableFuture<String> f3 = CompletableFuture.supplyAsync(CompletableFutureDemo::getResult);
		CompletableFuture<String> f4 = f3.whenComplete((result, error) -> {
			System.out.println("f3.result=" + result + ",error=" + error + "," + LocalDateTime.now());
		});
		
		System.out.println("f3=" + f3+","+LocalDateTime.now());
		System.out.println("f4=" + f4+","+LocalDateTime.now());

		Thread.sleep(2000);

		

	}
	
	private static String getResult() {
		try {
			Thread.sleep(1000);
			return LocalDateTime.now()+"";
		}catch(Throwable e) {
			//
			return LocalDateTime.now()+"";
		}
	}
}





https://gitee.com/dyyx/hellocode/blob/master/src/dyyx/conc/CompletableFutureDemo.java