A collection of RxUtils for Android

RxUtils.java

public class RxUtils {
    private RxUtils() {
    }

    @NonNull
    public static Func1<Observable<? extends Throwable>, Observable<?>> retryWithBackoff(
            final int maxAttempts, final long initialDelay, final TimeUnit unit) {
       return errors -> errors
               .zipWith(Observable.range(1, maxAttempts), (error, attempt) -> {
                   if (!isRetryable(error)) {
                       return new Pair<>(error, maxAttempts);
                   }
                   return new Pair<>(error, attempt);
               })
               .flatMap(pair -> {
                   final int attempt = pair.second;
                   if (attempt == maxAttempts) {
                       return Observable.error(pair.first);
                   }

                   final long delay = (long) Math.pow(initialDelay, attempt);
                   return Observable.timer(delay, unit);
               });
    }

    private static boolean isRetryable(@NonNull Throwable error) {
        if (error instanceof HttpException) {
            final HttpException httpException = (HttpException) error;
            final int code = httpException.code();
            return code == 500 || code == 503;
        } else {
            return false;
        }
    }
}