Java / J2EE Design Patterns

As software developers design and build different applications, we come across the same or similar problem domains. This leads us to find a solution for the same/similar problem everytime, and we end up "reinventing the wheel" again and again. It would be helpful to have a repository that discusses such common problem domains and proven solutions. It would be much better if such a repository discussed the problem domains, along with a solution best suited to solve the problem on hand. Such a solution could be the result of the hands-on experience of the development community.

1)Abstract Factory-PatternCreational patterns

2)ProtoType Pattern-Creational patterns

3)Factory Method Pattern-Creational patterns

4)Builder Pattern-Creational patterns

5)Visitor Pattern-Behavioral patterns

6)Template Method Pattern-Behavioral patterns

7)Strategy Pattern-Behavioral patterns

8)State Pattern-Behavioral patterns

9)Observer Pattern-Behavioral patterns

10)Memento Pattern -Behavioral patterns

11)Mediator Pattern-Behavioral patterns

12)Iterator Pattern-Behavioral patterns