Pattern Reminder: Strategy

Starting a new series to remember the good old gof design patterns. The STRATEGY Pattern will be my first entry.

Definition: "Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from the clients that use it." [Gamma]

Java Example: The client uses a capsuled family of algorithms. In this case we encapsulate a behaviour.

Client:

public abstract class Fighter {
FightingBehaviour fightingBehaviour;
public Fighter(){ };
public void fight(){fightingBehaviour.fight(); }
public void setFightingBehaviour(FightingBehaviour fb) {fightingBehaviour = fb;}
}


Client Implementations:


public class Boxer extends Fighter
{
public Boxer()
{
fightingBehaviour = new BoxingBehaviour();
}
}


Algorithm:


public interface FightingBehaviour {
public void fight();
}


Algorithm Implementation:

public class BoxingBehaviour implements FightingBehaviour {
public void fight() {
System.out.println("Raise fist!");
}
}


Test it:


Fighter fighter = new Boxer();
fighter.fight();


Thats basically it. It is now very easy to add new behaviours or fighters and change their algorithms.