Convert a listenable future to an rxjava-2 flowable or single

FlowableUtils.java

import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import io.reactivex.*;

/**
 * Created on 1/11/2017.
 */
public class FlowableUtils {

    public static <T> Single<T> fromFuture(ListenableFuture<? extends T> future) {
       /* Single.defer(() -> {
            Single.def
        })*/
        return Single.defer(() ->
                Single.create((SingleOnSubscribe<T>) e -> {
                    Futures.addCallback(future, new FutureCallback<T>() {
                        @Override
                        public void onSuccess(T result) {
                            e.onSuccess(result);
                        }

                        @Override
                        public void onFailure(Throwable t) {
                            e.onError(t);
                        }
                    });
                }));

    }

    public static <T> Flowable<T> flowableFromFuture(ListenableFuture<? extends T> future) {
        return Flowable.defer(() -> Flowable.create((FlowableOnSubscribe<T>) e -> {
            Futures.addCallback(future, new FutureCallback<T>() {
                @Override
                public void onSuccess(T result) {
                    e.onNext(result);
                    e.onComplete();
                }

                @Override
                public void onFailure(Throwable t) {
                    e.onError(t);
                }
            });
        }, BackpressureStrategy.BUFFER));
    }


    public static <T> Flowable<T> flowableFromFuture(ListenableFuture<? extends T> future, Scheduler scheduler) {
        return Flowable.defer(() -> Flowable.create((FlowableOnSubscribe<T>) e -> {
            Futures.addCallback(future, new FutureCallback<T>() {
                @Override
                public void onSuccess(T result) {
                    e.onNext(result);
                    e.onComplete();
                }

                @Override
                public void onFailure(Throwable t) {
                    e.onError(t);
                }
            });
        }, BackpressureStrategy.BUFFER))
                       .subscribeOn(scheduler);
    }
}