BerkeSoysal

public class MallardDuck extends Duck
{
    @Override
    public void display()
    {
        System.out.println("I'm a mallard duck");
    }
}

BerkeSoysal

public abstract class Duck
{
    public void swim()
    {
        System.out.println("i can swim.");
    }

    public void quack()
    {
        System.out.println("quack quack!");

BerkeSoysal

public interface FlyBehaviour
{
    void fly();
}

BerkeSoysal

public interface QuackBehavior
{
    void quack();
}

BerkeSoysal

public class Fly implements FlyBehaviour
{
    @Override
    public void fly()
    {
        System.out.println("I can fly.");
    }
}

BerkeSoysal

public abstract class Duck
{
    QuackBehavior quackBehavior;
    FlyBehaviour flyBehaviour;
    
    public void performQuack()
    {
        quackBehavior.quack();
    }

BerkeSoysal

public class MallardDuck extends Duck
{
    public MallardDuck()
    {
        this.quackBehavior = new Quack();
        this.flyBehaviour = new Fly();
    }

    @Override
    public void display()

BerkeSoysal

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

BerkeSoysal

public class Main {

    public static void main(String[] args) {

        Duck duck = new MallardDuck();
        duck.swim();
        duck.display();
        duck.performFly();
        duck.performQuack();
    }

BerkeSoysal

public class Main {

    public static void main(String[] args) {

        Duck duck = new MallardDuck();
        duck.swim(); // swimming
        duck.display(); // I'm a mallard duck
        duck.performFly(); // I can fly.
        duck.performQuack(); // Quack, quack!
        Duck otherduck = new RubberDuck();