Observable.java

Observable<Task> taskObservable = Observable
            .fromIterable(DataSource.createTasksList())
            .filter(new Predicate<Task>() {
                @Override
                public boolean test(Task task) throws Exception {
                    return task.isComplete();
                }
            })
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread());

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

            }
            @Override
            public void onNext(Task task) {
                Log.d(TAG, "onNext: This is a completed task: " + task.getDescription());
            }
            @Override
            public void onError(Throwable e) {

            }
            @Override
            public void onComplete() {

            }
        });