Note that I'm not a very good programmer, don't know very much about Java and math and didn't even know how to program a camera. But Jeffrey Ventrella helped me with some basics and also his document "Intuitive Computer Graphics Camera" helped me a lot: http://www.ventrella.com/Ideas/index.html
3D rendering helped me a lot to learn new programming languages because the visual outcome is more pleasing than seeing "hello world" in your console.
For those interested, here is the source of my Java "path tracer" (with Blender exporter): https://bitbucket.org/thuijzer/thrender001pt/
Note that I'm not a very good programmer, don't know very much about Java and math and didn't even know how to program a camera. But Jeffrey Ventrella helped me with some basics and also his document "Intuitive Computer Graphics Camera" helped me a lot: http://www.ventrella.com/Ideas/index.html