Create Observable using fromIterable method in RxJava

Constructs a sequence from a pre-existing source or generator type.
Signals the items from a java.lang.Iterable source (such as Lists, Sets or Collections or custom Iterables) and then completes the sequence.

List<String> list = new ArrayList<>();
list.add("1");
list.add("2");
list.add("3");

Observable<String> observable = Observable.fromIterable(list);

observable.subscribe(s -> {
    System.out.println(s);
});

References
https://github.com/ReactiveX/RxJava/wiki/Creating-Observables#fromiterable