CreateObservable.java

 final List<String> alphabets = getAlphabetList();

        /*
         * Observable.create() -> We will need to call the
         * respective methods of the emitter such as onNext()
         * & onComplete() or onError()
         *
         * */
        Observable observable = Observable.create(new ObservableOnSubscribe() {
            @Override
            public void subscribe(ObservableEmitter emitter) {

                try {

                    /*
                     * The emitter can be used to emit each list item
                     * to the subscriber.
                     *
                     * */
                    for (String alphabet : alphabets) {
                        emitter.onNext(alphabet);
                    }

                    /*
                     * Once all the items in the list are emitted,
                     * we can call complete stating that no more items
                     * are to be emitted.
                     *
                     * */
                    emitter.onComplete();

                } catch (Exception e) {

                    /*
                     * If an error occurs in the process,
                     * we can call error.
                     *
                     * */
                    emitter.onError(e);
                }
            }
        });


        /*
         * We create an Observer that is subscribed to Observer.
         * The only function of the Observer in this scenario is
         * to print the valeus emitted by the Observer.
         *
         * */
        Observer observer = new Observer() {
            @Override
            public void onSubscribe(Disposable d) {
                System.out.println("onSubscribe");
            }

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

            @Override
            public void onError(Throwable e) {
                System.out.println("onError: " + e.getMessage());
            }

            @Override
            public void onComplete() {
                System.out.println("onComplete");
            }
        };

        /*
         * We can call this method to subscribe
         * the observer to the Observable.
         * */
        observable.subscribe(observer);