PizzaDecorator.java

class Pizza {
    protected Pizza base;

    Pizza() {}

    Pizza(Pizza base) {
        this.base = base;
    }

    public int cost() {
        return 6; // Pizza dough with nothing on it will cost 6€
    }

    // Make System.out.println work like magic
    public String toString() {
        return this.cost() + "€";
    }
}

class WithGarlic extends Pizza {
    WithGarlic(Pizza base) {
        super(base);
    }

    public int cost() {
        return this.base.cost() + 1; // Additional 1€ for garlic
    }
}

class WithOnions extends Pizza {
    WithOnions(Pizza base) {
        super(base);
    }

    public int cost() {
        return this.base.cost() + 1; // Additional 1€ for onions
    }
}

class WithPepperonis extends Pizza {
    WithPepperonis(Pizza base) {
        super(base);
    }

    public int cost() {
        return this.base.cost() + 2; // Additional 2€ for pepperonis
    }
}

public class PizzaBusiness {
    public static void main(String[] args) {
        Pizza custom = new Pizza();
        custom = new WithGarlic(custom);
        custom = new WithOnions(custom);
        custom = new WithPepperonis(custom);
        // We could add 10 times onions for onion lovers 
        // .... 
        System.out.println("This pizza costs: "+custom);
    }
}