Strategy Design Pattern

strategy-pattern.java

public interface FlyBehavior {
    public void fly();
}

public interface QuackBehavior {
    public void quack();
}

public class FlyWithWings implements FlyBehavior {
    public void fly() { System.out.println("flying!"); }
}

public class FlyNoWay implements FlyBehavior {
    public void fly() { System.out.println("no flying!"); }
}

public class Quack implements QuackBehavior {
    public void quack() { System.out.println("Quack"); }
}

public class QuackMute implements QuackBehavior {
    public void quack() { System.out.println("Silence"); }
}

public abstract class Duck {
    FlyBehavior flyBehavior;
    QuackBehavior quackBehavior;
    
    public Duck() {}
    public void setFlyBehavior(FlyBehavior fb) { flyBehavior = fb; }
    public void setQuackBehavior(QuackBehavior qb) { quackBehavior = qb; }
    public abstract void display();
    public void performFly() { flyBehavior.fly(); }
    public void performQuack() { quackBehavior.quack(); }
    public void swim() { System.out.println("All ducks float!"); }
}

public class RedHeadDuck extends Duck {
    public RedHeadDuck() {
        flyBehavior = new FlyWithWings();
        quackBehavior = new Quack();
    }
    
    public void display() { System.out.println("Read Head Duck"); }
}

public class DecoyDuck extends Duck {
    public DecoyDuck() {
        setFlyBehavior(new FlyNoWay());
        setQuackBehavior(new QuackMute());
    }
    
    public void display() { System.out.println("Read Head Duck"); }
}