Prototype Design Pattern

Prototype design pattern is used when several similar objects of a class are required with slight or no modifications.

Let’s understand from this with an example. A client needs 100 cricket bats of exactly same dimensions. The only change can be the sticker on it. Some bats may have MRF sticker, some BDM, some A Sports, some Puma etc. So, the client goes to a cricket bat manufacturer with a prototype bat and asks it to make 100 similar bats. Let’s implement this scenario with Prototype pattern.

CricketBat.java

package com.sks.prototype;

public class CricketBat {

	private int length;
	private float width;
	private int handleLength;
	
	//sticker can be different
	private String sticker;
	
	public CricketBat clone() {
		return new CricketBat(this.length, this.width, this.handleLength);
	}

	public CricketBat(int length, float width, int handleLength) {
		super();
		this.length = length;
		this.width = width;
		this.handleLength = handleLength;
	}
	
	public void setSticker(String sticker) {
		this.sticker = sticker;
	}

	@Override
	public String toString() {
		return "CricketBat [length=" + length + ", width=" + width + ", handleLength=" + handleLength + ", sticker="
				+ sticker + "]";
	}
	
}

CricketBatManufacturer.java

package com.sks.prototype;

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

public class CricketBatManufacturer {

	enum stickers {
		MRF, CEAT, PUMA, ADDIDAS
	};

	public static List<CricketBat> makeBats(CricketBat prototypeBat, int quantity) {

		List<CricketBat> totalBats = new ArrayList<>();
		for (int i = 1; i <= quantity; i++) {
			totalBats.add(prototypeBat.clone());
		}

		return totalBats;
	}

	//apply stickers randomly from the enum list
	public static void applySticker(List<CricketBat> bats) {
		for (CricketBat b : bats) {
			int index = new Random().nextInt(stickers.values().length);
			String sticker = stickers.values()[index].name();
			b.setSticker(sticker);
		}
	}

}

CricketBatPrototypeTest.java

package com.sks.prototype;

import java.util.List;

public class CricketBatPrototypeTest {
	
	public static void main(String[] args) {
		
		CricketBat prototypeBat = new CricketBat(36, 4.25f, 11);
		int quantity = 10;
		List<CricketBat> bats = CricketBatManufacturer.makeBats(prototypeBat, quantity);
		
		CricketBatManufacturer.applySticker(bats);
		bats.forEach(b -> System.out.println(b));
		
	}
}

Output: