Hi... For this question u can answer like Singleton design 
pattern ,DAO and DTO,MVC.

The design pattern is broadly classified into 
1. Creational (Factory, Abstract Factory, Singleton 
Prototype, and Builder)
2. Structural (Composite)
3. Behavioural (Observer)

What is desing pattern?
  Commonly accepted solution for a particular problem is 
called design pattern.
We can classify the design patterns into two.
1. Java core patterns.
2. J2ee Design patters.

Core patterns.
1) Creational (Factory pattern, singleton pattern....etc)
2) Structural (Adaptor, Composite... etc)
3) Behavioural(Command, Template, Strategy... etc)

Entepise Patterns. (We can catagoize by layer)
1) Business Facade - Business Layer
2) Business Interface - Business Layer
3) DAO pattern - Persistent Layer
4) Composite View - Presentation Layer
5) synchronized - Presentation Layer
6) Service Locator... etc...

It is mainly divided into 3 types

1) creational
2) structural
3) Behavioral

It can also be divided into class and Object

            Creational       Structural          Behavioral


Class                         Adapter (Class)     Template

Object                        Adapter(Object)     Iterator
             Builder                              State
             Factory                             Strategy
                                                  Command
                                                  Mediator
                                                  Observer