How do I implement the decorator pattern in Java?

How do I implement the decorator pattern in Java?

The decorator pattern allows behavior to be added to individual objects, either statically or dynamically, without affecting the behavior of other objects from the same class. Would you like a code example?

Yes, please provide a code example.

Sure! Here's a simple example:

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

// Concrete component
class SimpleCoffee implements Coffee {
    public String getDescription() {
        return "Simple coffee";
    }
    public double cost() {
        return 2.00;
    }
}

// Decorator class
abstract class CoffeeDecorator implements Coffee {
    protected Coffee coffee;
    public CoffeeDecorator(Coffee coffee) {
        this.coffee = coffee;
    }
}

// Concrete decorators
class MilkDecorator extends CoffeeDecorator {
    public MilkDecorator(Coffee coffee) {
        super(coffee);
    }
    public String getDescription() {
        return coffee.getDescription() + ", milk";
    }
    public double cost() {
        return coffee.cost() + 0.50;
    }
}

class SugarDecorator extends CoffeeDecorator {
    public SugarDecorator(Coffee coffee) {
        super(coffee);
    }
    public String getDescription() {
        return coffee.getDescription() + ", sugar";
    }
    public double cost() {
        return coffee.cost() + 0.20;
    }
}

// Usage
public class Main {
    public static void main(String[] args) {
        Coffee coffee = new SimpleCoffee();
        coffee = new MilkDecorator(coffee);
        coffee = new SugarDecorator(coffee);
        System.out.println(coffee.getDescription() + " costs: " + coffee.cost());
    }
}

This will output: "Simple coffee, milk, sugar costs: 2.70".

What are the benefits of using the decorator pattern?

The decorator pattern provides flexibility in adding responsibilities to objects without modifying their structure. It promotes code reusability and adheres to the Single Responsibility Principle by allowing behavior to be added in a modular way.