Additional RxJava transformers

MyTransformers.java

	/**
	 * Transformer to concat a new observable based on the last element of the previous observable. Use the default value
	 * if the first observable is empty.
	 * 
	 * @param defaultValue
	 *          the default.
	 * @param nextObservable
	 *          function to create the next observable based on the current observable.
	 * @return the transformer.
	 */
	<T> Transformer<T, T> concatOnLast(T defaultValue, Func1<T, Observable<T>> nextObservable) {
		return source -> Observable.create(o -> {
			ConnectableObservable<T> s1 = source.publish();
			Observable<T> s2 = s1.lastOrDefault(defaultValue) // return a default value if source is empty.
				.flatMap(nextObservable); // init source2 here based on e.
			Observable.merge(s1, s2).subscribe(o);
			o.add(s1.connect());
		});
	}