Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it.
Participants
- Strategy: declares an interface common to all supported algorithms. Context uses this interface to call the algorithm defined by a ConcreteStrategy
- ConcreteStrategy: implements the algorithm using the Strategy interface
- Context: is configured with a ConcreteStrategy object. Maintains a reference to a Strategy object. May define an interface that lets Strategy access its data.
Code
public class Main { public static void main(String[] args) { Context context; context = new Context(new ConcreteStrategyA()); context.contextInterface(); context = new Context(new ConcreteStrategyB()); context.contextInterface(); } } public interface Strategy { void algorithmInterface(); } public class ConcreteStrategyA implements Strategy { @Override public void algorithmInterface() { System.out.println("Called ConcreteStrategyA.AlgorithmInterface()"); } } public class ConcreteStrategyB implements Strategy { @Override public void algorithmInterface() { System.out.println("Called ConcreteStrategyB.AlgorithmInterface()"); } } public class Context { private Strategy strategy; public Context(Strategy strategy) { this.strategy = strategy; } public void contextInterface() { strategy.algorithmInterface(); } } Output
Called ConcreteStrategyA.AlgorithmInterface() Called ConcreteStrategyB.AlgorithmInterface() 
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