Decorator Design Pattern

This pattern is part of the structural design patterns and is typically used when subclassing would become too complex, or when you want to enhance the functionality of certain objects without affecting others of the same class.

Component


package lld.designpattern.behaviour.decorator;

public interface Pizza {
    public double getPrice();
    public String getDescription();
}

ConcreteComponent


package lld.designpattern.behaviour.decorator;

public class BasePizza implements Pizza {
    @Override
    public double getPrice() {
        return 100.0;
    }

    @Override
    public String getDescription() {
        System.out.println("calling base pizza description");
        return "Plain Pizza";
    }
}

Decorator


package lld.designpattern.behaviour.decorator;

public abstract class PizzaDecorator implements Pizza {

    protected Pizza tempPizza;

    public PizzaDecorator(Pizza pizza){
        this.tempPizza =  pizza;
    }

    @Override
    public double getPrice() {
        return tempPizza.getPrice();
    }

    @Override
    public String getDescription() {
        return tempPizza.getDescription();
    }
}

ConcreteDecorator 1


package lld.designpattern.behaviour.decorator;

public class OlivesPizza extends PizzaDecorator{

    public OlivesPizza(Pizza pizza) {
        super(pizza);
    }

    @Override
    public String getDescription() {
        System.out.println("calling olive pizza description");
        return tempPizza.getDescription()+", Olive";
    }

    @Override
    public double getPrice() {
        return super.getPrice()+40.0;
    }
}

ConcreteDecorator 2


package lld.designpattern.behaviour.decorator;

public class CheesePizza extends PizzaDecorator{
    public CheesePizza(Pizza pizza) {
        super(pizza);
    }

    @Override
    public String getDescription() {
        return tempPizza.getDescription()+", Cheese";
    }

    @Override
    public double getPrice() {
        return tempPizza.getPrice()+30.0;
    }
}

💡

Why tempPizza is protected protected Pizza tempPizza;

Ans: So that only subclass can access this variable