How to implement a Scala Trait in Java code

Question

In scala, there is a trait like

trait Client {
  def get(requests: Seq[Request]): Future[Seq[Response]]
}

How to implement the class in Java with some fake implementation like return Future.successful(List.empty())?

I tried

class KVClient implements Client {
    @Override
    public Future<Seq<Response>> get(Seq<Request> requests) {
      return Future.successful(List.empty());
    }

But it didn't compile. Error is "KVClient is not abstract and does not override abstract method get(Seq) in Client"

Can you post exactly what is the compiler error you get?. In addition to this can you post the imports of the classes you are using? — JArgente
You can use ` Future future = CompletableFuture.completedFuture(value); ` to return a successful future. and please post the error as well — Geetika
The trait is trait Client def get(requests: Seq[Request]): Future[Seq[Response]] } I have KVClient which implements Client. ``` @Override public Future<Seq<Response>> get(Seq<Request> requests) { return Future.successful(List.empty()); } ``` The error is "KVClient is not abstract and does not override abstract method get(Seq<Request>) in Client" — Jing Huang

Dmitry Zagorulkin Dmitry Zagorulkin · Accepted Answer · 2020-02-04T09:32:27

if i understood you correctly you are trying to return result or error of response future.

Simple solution would be:

public CompletableFuture<Optional<?>> send() throws ExecutionException, InterruptedException {
      final CompletableFuture<Optional<?>> optionalCompletableFuture = CompletableFuture.supplyAsync(() -> "")
        .thenApplyAsync(f -> {
          if (isError(f)) {
            return Optional.empty();
          }
          return Optional.of(f);
        });
      return optionalCompletableFuture;

    }

How to implement a Scala Trait in Java code

1 Answers