---
layout: pattern
title: Strategy
folder: strategy
permalink: /patterns/strategy/
categories: Behavioral
tags:
 - Java
 - Difficulty-Beginner
 - Gang Of Four
---

**Also known as:** Policy

**Intent:** Define a family of algorithms, encapsulate each one, and make them
interchangeable. Strategy lets the algorithm vary independently from clients
that use it.

![alt text](./etc/strategy_1.png "Strategy")

**Applicability:** Use the Strategy pattern when

* many related classes differ only in their behavior. Strategies provide a way to configure a class either one of many behaviors
* you need different variants of an algorithm. for example, you might define algorithms reflecting different space/time trade-offs. Strategies can be used when these variants are implemented as a class hierarchy of algorithms
* an algorithm uses data that clients shouldn't know about. Use the Strategy pattern to avoid exposing complex, algorithm-specific data structures
* a class defines many behaviors, and these appear as multiple conditional statements in its operations. Instead of many conditionals, move related conditional branches into their own Strategy class

**Credits**

* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)