CODESAMPLE

Decorator - Java

Decorator Java

The Decorator pattern dynamically adds responsibilities to an object. It provides a flexible alternative to subclassing for extending functionality. Instead of inheriting from a base class to add behavior, you “wrap” the original object with decorator classes, each adding a specific responsibility. This implementation uses Java interfaces to define the core component and the decorator. Concrete components and decorators then implement these interfaces. The decorate() method allows for stacking decorators, enhancing the object’s behavior incrementally. This approach aligns with Java’s preference for composition over inheritance and promotes loose coupling.

// Component Interface
interface Coffee {
    String getDescription();
    double getCost();
}

// Concrete Component
class SimpleCoffee implements Coffee {
    @Override
    public String getDescription() {
        return "Simple coffee";
    }

    @Override
    public double getCost() {
        return 2.0;
    }
}

// Decorator Abstract Class
abstract class CoffeeDecorator implements Coffee {
    protected Coffee coffee;

    public CoffeeDecorator(Coffee coffee) {
        this.coffee = coffee;
    }

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

    @Override
    public double getCost() {
        return coffee.getCost();
    }
}

// Concrete Decorators
class MilkDecorator extends CoffeeDecorator {
    public MilkDecorator(Coffee coffee) {
        super(coffee);
    }

    @Override
    public String getDescription() {
        return coffee.getDescription() + ", with milk";
    }

    @Override
    public double getCost() {
        return coffee.getCost() + 0.5;
    }
}

class SugarDecorator extends CoffeeDecorator {
    public SugarDecorator(Coffee coffee) {
        super(coffee);
    }

    @Override
    public String getDescription() {
        return coffee.getDescription() + ", with sugar";
    }

    @Override
    public double getCost() {
        return coffee.getCost() + 0.2;
    }
}

// Example Usage
public class DecoratorExample {
    public static void main(String[] args) {
        Coffee coffee = new SimpleCoffee();
        System.out.println("Cost: $" + coffee.getCost() + ", Description: " + coffee.getDescription());

        coffee = new MilkDecorator(coffee);
        System.out.println("Cost: $" + coffee.getCost() + ", Description: " + coffee.getDescription());

        coffee = new SugarDecorator(coffee);
        System.out.println("Cost: $" + coffee.getCost() + ", Description: " + coffee.getDescription());
    }
}