Java and OpenGL Hiding cube faces not seen -

Java and OpenGL Hiding cube faces not seen -

i have made opengl 3d render engine in java uses vbo's , such optimization. i'm trying take farther hiding faces not seen user. i'm confused though, have far tried doing things scan see if blocks adjacent. decided whether render or not. not working @ all, blocks don't render now. whats efficient way of doing this, or know article read on?

java opengl 3d