I want pure code for a simple recommendation system (collaborative filtering) in Java or python. You are feel free to find a code from internet but it should be presented to me via a proper report (accompany with used data). Note that you are not allowed to use software packages/systems (like Apache Mahout, Python Crab etc.) for this project. Again, I ONLY want pure code.
Formal report is not necessary. Only something that shows what is happening. For example, commenting the functions/lines/classes is also good.