Java 8 optional: ifPresent return object orElseThrow exception

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Actually what you are searching is: Optional.map. Your code would then look like:

object.map(o -> "result" /* or your function */)
      .orElseThrow(MyCustomException::new);

I would rather omit passing the Optional if you can. In the end you gain nothing using an Optional here. A slightly other variant:

public String getString(Object yourObject) {
  if (Objects.isNull(yourObject)) { // or use requireNonNull instead if NullPointerException suffices
     throw new MyCustomException();
  }
  String result = ...
  // your string mapping function
  return result;
}

If you already have the Optional-object due to another call, I would still recommend you to use the map-method, instead of isPresent, etc. for the single reason, that I find it more readable (clearly a subjective decision ;-)).

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