four

Observable<Integer> values = Observable.create(o -> {
    o.onNext(1);
    o.onNext(1);
    o.onNext(2);
    o.onNext(3);
    o.onNext(2);
    o.onCompleted();
});

Subscription subscription = values
    .distinct()
    .subscribe(
        v -> System.out.println(v),
        e -> System.out.println("Error: " + e),
        () -> System.out.println("Completed")
    );