Java 8 - 并行调用方法异步并结合它们的结果

Question

我是Java 8并发功能的新手CompletableFuture,我希望你能帮助开始使用以下用例.

有一个叫做的服务TimeConsumingServices提供了耗时的操作,我想并行运行,因为它们都是独立的.

interface TimeConsumingService {

  default String hello(String name) {
    System.out.println(System.currentTimeMillis() + " > hello " + name);
    return "Hello " + name;
  }
  default String planet(String name) {
    System.out.println(System.currentTimeMillis() + " > planet " + name);
    return "Planet: " + name;
  }
  default String echo(String name) {
    System.out.println(System.currentTimeMillis() + " > echo " + name);
    return name;
  }

  default byte[] convert(String hello, String planet, String echo) {
    StringBuilder sb = new StringBuilder();
    sb.append(hello);
    sb.append(planet);
    sb.append(echo);
    return sb.toString().getBytes();
  }
}

到目前为止,我实现了以下示例,并设法并行调用所有三种服务方法.

public class Runner implements TimeConsumingService {

  public static void main(String[] args) {
    new Runner().doStuffAsync();
  }

  public void doStuffAsync() {
    CompletableFuture<String> future1 = CompletableFuture.supplyAsync(() -> this.hello("Friend"));
    CompletableFuture<String> future2 = CompletableFuture.supplyAsync(() -> this.planet("Earth"));
    CompletableFuture<String> future3 = CompletableFuture.supplyAsync(() -> this.echo("Where is my echo?"));

    CompletableFuture.allOf(future1, future2, future3).join();
  }
}

有没有办法收集每个服务调用的返回值并调用该方法byte[]‘ convert(String, String, String)？

Answer 1

要在返回结果后合并结果,您可以执行以下操作

CompletableFuture<byte[]> byteFuture = CompletableFuture.allOf(cf1, cf2, cf3)
                     .thenApplyAsync(aVoid -> convert(cf1.join(), cf2.join(), cf3.join()));
byte[] bytes = byteFuture.join();

这将运行你所有的期货,等待它们全部完成,然后一旦它们全部完成将调用convert你提到的方法.

Answer 2

加入后，您可以简单地get()从以下值中获取值future1：

String s1 = future1.get()

等等