code: public static <T> EventStream<T> valuesOf(ObservableValue<T> observable) {
          return new EventStreamBase<T>() {
              @Override
              protected Subscription observeInputs() {
                  ChangeListener<T> listener = (obs, old, val) -> emit(val);
                  observable.addListener(listener);
                  return () -> observable.removeListener(listener);
              }
  
              @Override
              protected void newObserver(Consumer<? super T> subscriber) {
                  subscriber.accept(observable.getValue());
              }
          };
      }
docs: Creates an event stream that emits the value of the given
  {@code ObservableValue} immediately for every subscriber and then on
  every change.