SubjectExample.java

        /*
         * Step 1: Create an observable that emits an integer
         * from 1 to 5
         *  */
        Observable<Integer> observable = Observable.range(1, 5)
                .subscribeOn(Schedulers.io());

        /*
         * Step 2: Create a subject that observes
         * this emission from the observable. In this scenario,
         * the subject acts an an observer since it observes the
         * changes to the Observable.
         *  */
        ReplaySubject<Integer> subject = ReplaySubject.create();
        observable.subscribe(subject);


        /*
         * Step 3: In this scenario, the subject acts an an Observable,
         * since it emits each item from the original Observable.
         *  */
        subject.subscribe(s -> System.out.println("subscriber one: " + s));
        subject.subscribe(s -> System.out.println("subscriber two: " + s));