BuilderDesignPattern.java

package coreJava;

import java.util.ArrayList;
import java.util.List;

// It is used to build a complex object using simple objects and using a step by step approach.
// This design pattern comes under creational pattern as this pattern 
// provides one of the best way to create an object.
interface Item {
	public String name();

	public Packing packing();

	public float price();
}

interface Packing {
	public String pack();
}

class Wrapper implements Packing {
	@Override
	public String pack() {
		return "Wrapper";
	}
}

class Bottle implements Packing {
	@Override
	public String pack() {
		return "Bottle";
	}
}

abstract class Burger implements Item {
	@Override
	public Packing packing() {
		return new Wrapper();
	}

	@Override
	public abstract float price();
}

abstract class ColdDrink implements Item {
	@Override
	public Packing packing() {
		return new Bottle();
	}

	@Override
	public abstract float price();
}

class VegBurger extends Burger {
	@Override
	public float price() {
		return 25.0f;
	}

	@Override
	public String name() {
		return "Veg Burger";
	}
}

class ChickenBurger extends Burger {
	@Override
	public float price() {
		return 50.5f;
	}

	@Override
	public String name() {
		return "Chicken Burger";
	}
}

class Coke extends ColdDrink {
	@Override
	public float price() {
		return 30.0f;
	}

	@Override
	public String name() {
		return "Coke";
	}
}

class Pepsi extends ColdDrink {
	@Override
	public float price() {
		return 35.0f;
	}

	@Override
	public String name() {
		return "Pepsi";
	}
}

class Meal {
	private List<Item> items = new ArrayList<Item>();

	public void addItem(Item item) {
		items.add(item);
	}

	public float getCost() {
		float cost = 0.0f;

		for (Item item : items) {
			cost += item.price();
		}
		return cost;
	}

	public void showItems() {

		for (Item item : items) {
			System.out.print("Item : " + item.name());
			System.out.print(", Packing : " + item.packing().pack());
			System.out.println(", Price : " + item.price());
		}
	}
}

class MealBuilder {

	public Meal prepareVegMeal() {
		Meal meal = new Meal();
		meal.addItem(new VegBurger());
		meal.addItem(new Coke());
		return meal;
	}

	public Meal prepareNonVegMeal() {
		Meal meal = new Meal();
		meal.addItem(new ChickenBurger());
		meal.addItem(new Pepsi());
		return meal;
	}
}

public class BuilderDesignPattern {
	public static void main(String[] args) {

		MealBuilder mealBuilder = new MealBuilder();

		Meal vegMeal = mealBuilder.prepareVegMeal();
		System.out.println("Veg Meal");
		vegMeal.showItems();
		System.out.println("Total Cost: " + vegMeal.getCost());

		Meal nonVegMeal = mealBuilder.prepareNonVegMeal();
		System.out.println("\n\nNon-Veg Meal");
		nonVegMeal.showItems();
		System.out.println("Total Cost: " + nonVegMeal.getCost());
	}
}


//Output
//----------------
//Veg Meal
//Item : Veg Burger, Packing : Wrapper, Price : 25.0
//Item : Coke, Packing : Bottle, Price : 30.0
//Total Cost: 55.0
//
//
//Non-Veg Meal
//Item : Chicken Burger, Packing : Wrapper, Price : 50.5
//Item : Pepsi, Packing : Bottle, Price : 35.0
//Total Cost: 85.5