Strategy Pattern




The Strategy Pattern defines a family of algorithms, encapsulates each one, and makes them interchangeable. Strategy lets the algorithm vary independently from clients that use it.

Example

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public interface IBehaviourStrategy {
 public void run();
 public void fly();
 public void wild();
 public void swim();
}
==========
public class PetAnimalBehaviour implements IBehaviourStrategy{
  
 @Override
 public void run() {
  System.out.println("I can run medium-fast."); 
   }

  @Override
 public void fly() {
  System.out.println("\nI cannot Fly.");
 }

  @Override
 public void wild() {
  System.out.println("My Behaviour never seems wild.");
 }

  @Override
 public void swim() {
  System.out.println("I can swim short distance.");
 }
}
===========
public class WildAnimalBehaviour implements IBehaviourStrategy {

  @Override
 public void run() {
  System.out.println("I can Run very fast");
 }

  @Override
 public void fly() {
  System.out.println("\nI cannot Fly. But I run like I fly.");  
 }

  @Override
 public void wild() {
  System.out.println("I am wild and Healthy");
 }

  @Override
 public void swim() {
  System.out.println("I can swim long river");
 }
}
==========
public class Cow extends Animal{
 Cow(){
  behaviour =  new PetAnimalBehaviour();
 }
}
==========
 public class Tiger extends Animal { 
 Tiger(){
  behaviour = new WildAnimalBehaviour();
 }
}
==========
public abstract class Animal {
 IBehaviourStrategy behaviour;
 
 Animal(){}
 
 public void checkBehaviours(){
  behaviour.fly();
  behaviour.run();
  behaviour.swim();
  behaviour.wild();
 }
}
==========
public class StrategyPatternFlight {
 public static void main(String[] bag){
  
  Animal wildAnimals = new Tiger();
  wildAnimals.checkBehaviours();
  
  Animal cow = new Cow();
  cow.checkBehaviours();
 }
}
==========