Composite Design Pattern

Composite design pattern is used when we need to represent a part-whole hierarchy. For example, you go to a restaurant, there the attendant can give you a menu booklet that contains everything. On the contrary, at some restaurants you can have separate menu for food, separate for desserts, and a separate one for drinks. The all 3 will collectively constitute the entire menu of the restaurant.

In the below example, we will implement the similar solution.

FoodType interface

package com.sks.composite;

public interface FoodType {
	
	void getInfo();

}

FoodItem abstract class

package com.sks.composite;

public abstract class FoodItem implements FoodType {
	
	protected String name;
	protected int price;
	
	public FoodItem(String name, int price) {
		super();
		this.name = name;
		this.price = price;
	}

	@Override
	public String toString() {
		return "FoodItem [name=" + name + ", price=" + price + "]";
	}

}

GravyItem.java

package com.sks.composite;

public class GravyItem extends FoodItem {
	
	public GravyItem(String name, int price) {
		super(name, price);
	}

	@Override
	public void getInfo() {
		System.out.println("Item Name : " + this.name);
		System.out.println("Price : " + this.price);
	}	
}

Bread.java

package com.sks.composite;

public class Bread extends FoodItem {

	@Override
	public void getInfo() {
		System.out.println("Item Name : " + this.name);
		System.out.println("Price : " + this.price);
	}
	
	public Bread(String name, int price) {
		super(name, price);
	}
	
}

Sweet.java

package com.sks.composite;

public class Sweet extends FoodItem {

	@Override
	public void getInfo() {
		System.out.println("Item Name : " + this.name);
		System.out.println("Price : " + this.price);
	}
	
	public Sweet(String name, int price) {
		super(name, price);
		// TODO Auto-generated constructor stub
	}
	
}

Menu.java

package com.sks.composite;

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

public class Menu implements FoodType {

	private List<FoodType> menu = new ArrayList<>();

	@Override
	public void getInfo() {
		for (FoodType f : menu) {
			f.getInfo();
		}
	}

	public void add(FoodType foodType) {
		menu.add(foodType);
	}

}

CompositePatternTest

package com.sks.composite;

public class CompositePatternTest {

	public static void main(String[] args) {
		
		FoodItem dal = new GravyItem("Dal Tadka", 250);
		FoodItem paneer = new GravyItem("Kadhai Paneer", 350);
		FoodItem roti = new Bread("Tandoori Roti", 50);
		
		Menu lunchMenu = new Menu();
		lunchMenu.add(dal);
		lunchMenu.add(roti);
		lunchMenu.add(paneer);
		
		FoodItem iceCream = new Sweet("Mango ice cream", 200);
		FoodItem gulabJamun = new Sweet("Gulab Jamun", 100);
		
		Menu dessertMenu = new Menu();
		dessertMenu.add(iceCream);
		dessertMenu.add(gulabJamun);
		
		Menu mainMenu = new Menu();
		mainMenu.add(lunchMenu);
		mainMenu.add(dessertMenu);
		
		mainMenu.getInfo();
		
	}
}

Output :