Groovy: Overriding “Plus” operator in a class with interesting example

26 / Sep / 2012 by Imran Mir 2 comments

Have you ever wondered how to overload “plus” operator in Groovy ? It is as easy as adding toppings to your favourite pizza. Let me explain. Let us taka a class for Pizza:


class Pizza {
    String name
    List<Topping> toppings
    double price


And another for the Topping:

class Topping {
    String name
    double price

Now to add toppings to the favourite pizza, let us overload the plus operator in Pizza class like this:

//Method with name "plus" will override the "+" operator. It will return a new pizza with the Toppings added.
    Pizza plus(Topping topping) {
        new Pizza(name: name, toppings: toppings + [topping], price: price + topping.price)

Let us order a pizza:

Pizza pizza = new Pizza(name: "Veg Extravaganza Pizza", price: 323.32, toppings: [])

And our favourite toppings as well:

Topping cheeseBurst = new Topping(name: "cheese Burst", price: 80)
Topping extraCheese = new Topping(name: "Extra Cheese", price: 40.43)
Topping jalepenos = new Topping(name: "Jallepenos", price: 50.33)
Topping capsicum = new Topping(name: "capsicum", price: 20.32)

Can’t wait to add them all:

Pizza specialPizza = pizza + cheeseBurst + extraCheese + jalepenos + capsicum

Let us unbox our pizza:

println (specialPizza)

Pizza(Veg Extravaganza Pizza, [Topping(cheese Burst, 80.0), Topping(Extra Cheese, 40.43), Topping(Jallepenos, 50.33), Topping(capsicum, 20.32)], 514.4)

Isn’t it mouth watering.

Hope this helps.


Imran Mir


comments (2)

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