Only catch exceptions of a specific type in RxJava 2

Question

I'm just learning RxJava 2 and I would like catch exceptions only of a specific type and return an Observable. Essentially, I want onErrorResumeNext() to only catch a specific exception class, but it looks like she doesn't work that way.

What are my options for achieving this behavior in RxJava 2? Just use onErrorResumeNext(), handle my specific exception and rethrow the others? Something like:

.onErrorResumeNext(throwable -> throwable instanceof NotFoundException ? Observable.empty() : Observable.error(throwable));

Answer 1

I would return Observable.empty instead just null

.onErrorResumeNext(t -> t instanceof NullPointerException ? Observable.empty():Observable.error(t))

Answer 2

Just use composition:

public <T> Function<Throwable, Observable<T>> whenExceptionIsThenIgnore(Class<E> what) {
  return t -> {
    return what.isInstance(t) ? Observable.empty() : Observable.error(t);
  };
}

Then use like this:

Observable.from(...).flatMap(...)
.onErrorResumeNext(whenExceptionIsThenIgnore(IllegalArgumentException.class))
.onErrorResumeNext(whenExceptionIsThenIgnore(IOException.class))
...

See also this answer on selectively handling exceptions.