Java API (not recommended): Callback for the Future.filter operation that creates a new Future which will conditionally contain the success of another Future.

Unfortunately it is not possible to express the type of a Scala filter in Java: Function1[T, Boolean], where “Boolean” is the primitive type. It is possible to use Future.filter by constructing such a function indirectly:

import static akka.dispatch.Filter.filterOf;
Future<String> f = ...;
f.filter(filterOf(new Function<String, Boolean>() {
  @Override
  public Boolean apply(String s) {
    ...
  }
}));

However, Future.filter exists mainly to support Scala’s for-comprehensions, thus Java users should prefer Future.map, translating non-matching values to failure cases.