rx.java

        Observable<String> input = Observable.create(new ObservableOnSubscribe<String>() {
            @Override
            public void subscribe(ObservableEmitter<String> e) throws Exception {
                BufferedReader bfr = new BufferedReader(new InputStreamReader(System.in));
                while (true) {
                    e.onNext(bfr.readLine());
                }
            }
        });

        Observable<String> breaker = input.filter((String s) -> { return s.startsWith("END"); });

        Observable<String> text = input.takeUntil(breaker);

...