What is a design pattern? Why should you care? What it the power of design patterns? How do design patterns tie into object oriented programming? If I'm using objects in my code, isn't that object oriented programming? (The answer is not necessarily!) When should I use them? Design Patterns are great but the temptation is to use Design Patterns as a golden hammer. This can lead to unnecessarily complicated, over-engineered code in an effort to be flexible and ready for the future. That sounds reasonable - if you happen to be a psychic. More commonly, you will refactor to a pattern when the code (that you’ve written simply and minimally) demands it. We'll talk about why you should know common design patterns, why they are powerful, how they relate to object oriented principles, different composite refactorings that will move you to (and sometimes away) from patterns and the smells that help you know when to apply them.