When to use zip() instead of zipWith() RxJava

Question

Is there any semantic difference in pairwise composing with zip() vs. zipWith() in RxJava? Is the choice between the static zip and the .zipWith purely stylistic?

Answer 1

Convenience and context.

The static zip is useful when you have two sources already assembled and now you want to zip them together. Most of the time they are themselves long chains or come from all over the place.

Observable<T1> source1 = op().op().op().op().op();
Observable<T2> source2 = op().op().op().op().op();

Observable.zip(source1, source2, (a, b) -> a + b);

The instance zipWith is useful when one of the sources is longer while the other is shorter. At that point, it is more convenient to zip with the shorter one.

public Observable<R> withIndex(Observable<T> source, Func2<Integer, T, R> func) {
    return source.zipWith(Observable.range(0, Integer.MAX_VALUE),
         (t, idx) -> func(idx, t));
}