I have now become good in Java
i want the easiest way to game programming ...
Unfortunately, when it comes to game programming, there isn't really a 'real' easy way out. You could use numerous libraries, engines, and other utilities to help you accomplish the goal and while there is nothing wrong with using other utilities to help you build a game, you cannot build a game just by using those programs.
I can only recommend that you start simple with programming basics and than some various Java lessons. I'd start with Java2D and than if you need something more you can move onto something like libGDX, LWJGL, or any other java openGL library/framework/engine. Start small and simple and work your way up. Trust me, in the end you'll be a much better developer in general if you do something like this.