A design patterns are well-proved solution for solving the specific problem/task. We must use the design patterns during the analysis and requirement phase of SDLC(Software Development Life Cycle).

In core java, there are mainly three types of design patterns, which are further divided into their sub-parts:

1. Creational Design Pattern
   1.1 Factory Pattern
   1.2 Abstract Factory Pattern
   1.3 Singleton Pattern
   1.4 Prototype Pattern
   1.5 Builder Pattern
2. Structural Design Pattern
   2.1 Adapter Pattern
   2.2 Bridge Pattern
   2.3 Composite Pattern
   2.4 Decorator Pattern
   2.5 Facade Pattern
   2.6 Flyweight Pattern
   2.7 Proxy Pattern
3. Behavioral Design Pattern
   3.1 Chain Of Responsibility Pattern
   3.2 Command Pattern
   3.3 Interpreter Pattern
   3.4 Iterator Pattern
   3.5 Mediator Pattern
   3.6 Memento Pattern
   3.7 Observer Pattern
   3.8 State Pattern
   3.9 Strategy Pattern
   3.10 Template Pattern
   3.11 Visitor Pattern