RxJava collect() example. Converting a list of phrases into a list of their IDs only.

RxJavaCollectExample.java

@Override
public void onNext(ArrayList<Phrase> phrases) {
    ArrayList<Integer> phraseIDs = new ArrayList<>();
    Observable
        .from(phrases)
        .collect(phraseIDs, new Action2<ArrayList<Integer>, Phrase>() {
            @Override
            public void call(ArrayList<Integer> integers, Phrase phrase) {
                integers.add(phrase.getId());
            }
        })
        .subscribe();
}

        List<Integer> phraseIDs = new ArrayList<>();
        Observable.fromArray(phrases)
                .flatMapIterable(x -> x)
                .collect(() -> phraseIDs, (l, p) -> l.add(p.getId()))
                .subscribe();

Thanks, this was helpful.