How to get started?

I am a programmer who knows java and wants to learn game programming. Should I use OpenGL or DirectX? How should I get started?

Both APIs are good ways to learn programming a GPU. Thought with java as background, I would sugguest to use OpenGL, atleast you stick to platform independency and java/DirectX sounds wrong (Oracle/Microsoft..naah ).

If you are going to be programming games in Java I recommend The Lightweight Java Game Library (LWJGL). It uses OpenGL for rendering and you can also use OpenAL for audio if you want.

I suggest that you should read the book which called "Windows Game Programming Gurus".It includes many skills of how to make a whole PC game such as 2D and 3D technology,sound inserting and so on.The DirectX is surely the first selection you should conside .If you decide to make the game ,you must stick to it.

Thanks!(I think ill stick to DirectX as I use mainly Windows) Are there any books for learning C++? Is it similar to java?

"C++Primer" is pretty good.Although the Author is sometimes wordy,it's surely detailed and careful.C++ can be used to the large game programming for it's fast operation efficiency.Jave is easy to write and learn,but i think it's suitable to the mobile phone game.You know whatever SDK or language you like,the game programming is the same.If you are in command of one language , another will be easily to learn.