Design Pattern - : * A design pattern is gerneral repeatable solution to a commonally occouring problem in software design. * A design pattern isn't a finished design that can be transfer directly into code.it is description or template for how to solve a problem that can be used in many different situation.
1. Creational Design pattern :Deal with object creation method . Ex. Factory pattern, Singleton and Observer design pattern
2. Structure Design pattern : deal with decoupling interface and implementation of class and object. Ex. Facade
3. Behavioural Design pattern : Identify common community pattern betweenobjects. Ex.Template method