UsingObservable.java

        Observable.using(
                new Callable<String>() {
                    @Override
                    public String call() throws Exception {
                        return "Example";
                    }
                },

                new Function<String, ObservableSource<Character>>() {
                    @Override
                    public ObservableSource<Character> apply(String s) {
                        return Observable.create(o -> {
                            for (Character c : s.toCharArray()) {
                                o.onNext(c);
                            }
                            o.onComplete();
                        });
                    }
                },

                new Consumer<String>() {
                    @Override
                    public void accept(String s) {
                        System.out.println("Disposable: " + s);
                    }
                }
        )

                .subscribe(new Observer<Character>() {
                    @Override
                    public void onSubscribe(Disposable d) {

                    }

                    @Override
                    public void onNext(Character character) {
                        System.out.println("onNext: " + character);
                    }

                    @Override
                    public void onError(Throwable e) {

                    }

                    @Override
                    public void onComplete() {

                    }
                });