Decorator pattern

// The abstract Coffee class defines the functionality of Coffee implemented by decorator
public abstract class Coffee {
    public abstract double getCost(); // Returns the cost of the coffee
    public abstract String getIngredients(); // Returns the ingredients of the coffee
}
 
// Extension of a simple coffee without any extra ingredients
public class SimpleCoffee extends Coffee {
    public double getCost() {
        return 1;
    }
 
    public String getIngredients() {
        return "Coffee";
    }
}

// Abstract decorator class - note that it extends Coffee abstract class
public abstract class CoffeeDecorator extends Coffee {
    protected final Coffee decoratedCoffee;
    protected String ingredientSeparator = ", ";
 
    public CoffeeDecorator (Coffee decoratedCoffee) {
        this.decoratedCoffee = decoratedCoffee;
    }
 
    public double getCost() { // Implementing methods of the abstract class
        return decoratedCoffee.getCost();
    }
 
    public String getIngredients() {
        return decoratedCoffee.getIngredients();
    }
}

// Decorator Milk that mixes milk with coffee.
// Note it extends CoffeeDecorator.
class Milk extends CoffeeDecorator {
    public Milk (Coffee decoratedCoffee) {
        super(decoratedCoffee);
    }
 
    public double getCost() { // Overriding methods defined in the abstract superclass
        return super.getCost() + 0.5;
    }
 
    public String getIngredients() {
        return super.getIngredients() + ingredientSeparator + "Milk";
    }
}
 
// Decorator Whip that mixes whip with coffee.
// Note it extends CoffeeDecorator.
class Whip extends CoffeeDecorator {
    public Whip (Coffee decoratedCoffee) {
        super(decoratedCoffee);
    }
 
    public double getCost() {
        return super.getCost() + 0.7;
    }
 
    public String getIngredients() {
        return super.getIngredients() + ingredientSeparator + "Whip";
    }
}
 
// Decorator Sprinkles that mixes sprinkles with coffee.
// Note it extends CoffeeDecorator.
class Sprinkles extends CoffeeDecorator {
    public Sprinkles (Coffee decoratedCoffee) {
        super(decoratedCoffee);
    }
 
    public double getCost() {
        return super.getCost() + 0.2;
    }
 
    public String getIngredients() {
        return super.getIngredients() + ingredientSeparator + "Sprinkles";
    }
}

public class Main {
 
    public static final void main(String[] args) {
    Coffee c = new SimpleCoffee();
    System.out.println("Cost: " + c.getCost() + "; Ingredients: " + c.getIngredients());
 
    c = new Milk(c);
    System.out.println("Cost: " + c.getCost() + "; Ingredients: " + c.getIngredients());
 
    c = new Sprinkles(c);
    System.out.println("Cost: " + c.getCost() + "; Ingredients: " + c.getIngredients());
 
    c = new Whip(c);
    System.out.println("Cost: " + c.getCost() + "; Ingredients: " + c.getIngredients());
 
    // Note that you can also stack more than one decorator of the same type
    c = new Sprinkles(c);
    System.out.println("Cost: " + c.getCost() + "; Ingredients: " + c.getIngredients());
    }
 
}

Cost: 1.0; Ingredients: Coffee
Cost: 1.5; Ingredients: Coffee, Milk
Cost: 1.7; Ingredients: Coffee, Milk, Sprinkles
Cost: 2.4; Ingredients: Coffee, Milk, Sprinkles, Whip
Cost: 2.6; Ingredients: Coffee, Milk, Sprinkles, Whip, Sprinkles