code: public static <T> com.google.common.util.concurrent.ListenableFuture<T> toGuavaListenableFuture(ListenableFuture<T> springListenableFuture) {
              return GuavaFutureUtils.createListenableFuture(SpringFutureUtils.createValueSourceFuture(springListenableFuture));
      }
docs: Converts Spring 4 {@link org.springframework.util.concurrent.ListenableFuture}
  to Guava {@link com.google.common.util.concurrent.ListenableFuture}.