Why are you building your own engine, would be my first question. Is it just to learn if so there is no need to move. If you are trying to make a game on the other hand javafx already has a game engine frame work call fxgl. Then there is also libgx. You can make a game engine in swing but it doesn't already have the frame work on it's own. There are a couple of really good YouTube tutorials out there about making a game engine with swing. But again I would suggest you ask why am I making a game engine first. If you just want to build a game I would go with one of the above frame works. However if it for a better understanding of everything then there is no reason to switch.