Obsessing over Design Patterns! I would not worry too much about design patterns to begin with. It is good if you are aware of their existence so that you will know what other members of your team talk about, but what is important right now is just exploring the Core Java APIs. When you feel comfortable with them I'd really put an effort into learning how to write clean and self-documenting code. This will save you a lot of time and effort in the future when you go back and need to remember what you were doing.
