MainActivity.java

  Observable<Integer> observer1 = Observable.from(new Integer[]{1, 2, 3, 4, 5});
  Observable<Integer> observer2 = Observable.from(new Integer[]{6, 7, 8, 9, 10});

  Observable.merge(observer1, observer2)
          .subscribeOn(Schedulers.newThread())
          .observeOn(Schedulers.io())
          .subscribe(new Action1<Integer>() {
              @Override
              public void call(Integer integer) {
                  Log.d("Observer", "Output:" + integer);
              }
          });