Encapsulate what varies.
Favor composition over inheritance.
Program to interface, not implementation.
Strive for loosely coupled designs between objects that interact.
Classes should open for extension but closed for modification.
Depend on abstractions.Do not depend on concrete classes.
Only talk to your friends.
Don't call us, we will call you.
A class should have only one reason to change.
Strategy - defines a family of algorithm, encapsulates each one, and makes them interchangeable.Strategy lets the algorithm vary independent form client that use it.
Observer - defines a one-to-many dependency between objects so that when one objects changes state, all its dependents are notified and updated automatically.
Decorator - Attach additional responsibilities to an object dynamically.Decorators provide a flexible alternative to subclassing for extending functionality.
Abstract Factory - Provide an interface for creating families of related or dependent objects without specifying their concrete classes.
Factory Method - Define an interface for creating an object, but let subclasses decide which class to instantiate.Factory Method lets a class defer instantiation to the subclasses.
Singleton - Ensure a class only has one instance and provide a global point of access to it.
Command - Encapsulates a request as an objects, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations.
Adapter - Converts the interface of a class to another interface clients expects.Let classes work together that couldn't otherwise because of incompatible interface.
Facade - Provides a unified interface to a set of interface in a subsystem.Facade defines a higher-level interface that makes the subsystem easier to use.
Template Method - Define the skeleton of an algorithm in an operation, deferring some steps to subclasses.Template Method lets subclasses redefine certain steps of an algorithm without changing the algorithm's structure.
Iterator - Provide a way to access the elements of an aggregate objects sequentially without exposing its underlying representation.
Composite - Compose objects into tree structure to represent part-whole hierarchies.Composite let clients treat individual objects and compositions of objects uniformly.
State - Allow an object to alter its behavior when its internal state changes.The object will appear to change its class.
Proxy - Provide a surrogate or placeholder for another object to control access to it.
A Compound Pattern combines two or more patterns into a solution that solves a recurring or general problem.
Chain of Responsibility
《Head First Design Pattern》