Assuming you are on a PC and not an Android device (they are also written with Java) look up JOGL, the Java OpenGL interface. Everything you need is under javax.media.opengl.*.
So from what I am understanding, it uses the CPU by default for loading image and running the game unless I make it explicitly I want to use hardware acceleration from standard pure Java?
I see. Would I be at a disadvantage if I do not have any knowledge on OpenGL? Is that really true?
This source says "This allows computer graphics programmers to use the object-oriented tools for Java with hardware-accellerated 2D and 3D graphics while leveraging their existing knowledge of OpenGL."