Introduction to design patterns Prototype

Introduction to design patterns Prototype

Overview

What is a Prototype pattern?

--Prototype: Create an instance from "prototype". Not from class. --There is an entity class that implements the Cloneable interface and can clone itself.

Miso

Actions such as drawing a rectangle are common, but at that time

-Rectangle surrounded by "/" -Rectangle surrounded by "*" --Rectangle surrounded by "x"

When there are three templates that are divided like this, there is no point in making each in a separate class.

Classify only the shape of the figure to be drawn, and map the line type to Client as the same class.

And when repeating the same "drawing a triangle with the line of" / "", you can clone a new instance from the Prototype instance registered as a template and use it.

Conceptual diagram

--Client calls Prototype --ConcretePrototype that implements Prototype is cloned by createClone

Implementation drawing

Character

--framework package --Product interface: Inherit Cloneable --Manager class: Cloneable is stored in Map and cloned --entity package --Main: Entry point --MessageBox class: Implemented Product. Draw Rectangle / ConcreteProduct --UnderLinePen class: Implemented Product. Underline / ConcreteProduct

Implementation source

Product

Product

package prototype.product.frameworks;

public interface Product extends Cloneable{
	public abstract void use(String s);
	public abstract Product createClone();

}

Manager

package prototype.product.frameworks;

import java.util.HashMap;

public class Manager {

	private HashMap<String, Cloneable> showcase = new HashMap<>();
	public void register(String name, Cloneable prototype) {
		showcase.put(name, prototype);
	}

	public Product create(String protoname) {
		Product p = (Product)showcase.get(protoname);
		return p.createClone();
	}

}

MessageBox

package prototype.product.entity;

import prototype.product.frameworks.Product;

public class MessageBox implements Product {
	private char decoChar;

	public MessageBox(char decoChar) {
		this.decoChar = decoChar;
	}

	@Override
	public void use(String s ) {
		int length = s.getBytes().length;
		for (int i = 0; i < length+4; i++) {
			System.out.print(decoChar);
		}
		System.out.println("");
		System.out.println(decoChar+" "+s + " " +decoChar);
		for (int i = 0; i <length+4; i++) {
			System.out.print(decoChar);
		}
		System.out.println("");
	}

	@Override
	public Product createClone() {
		Product product = null;
		try {
			product= (Product)clone();
		}catch (CloneNotSupportedException e) {
			e.printStackTrace();
		}
		return product;
	}
}

UnderLinePen

package prototype.product.entity;

import prototype.product.frameworks.Product;

public class UnderLinePen implements Product{
	private char ulChar;
	public UnderLinePen(char ulChar) {
		this.ulChar = ulChar;
	}
	@Override
	public void use(String s) {
		int length = s.getBytes().length;
		System.out.println("¥ "+s+" ¥");
		for (int i = 0; i < length+4; i++) {
			System.out.print(ulChar);
		}
		System.out.println("");
	}

	@Override
	public Product createClone() {
		Product product = null;
		try {
			product = (Product) clone();
		}catch (CloneNotSupportedException e) {
			e.printStackTrace();
		}
		return product;
	}

}

Main

package prototype.product.entity;

import prototype.product.frameworks.Manager;
import prototype.product.frameworks.Product;

public class Main {
	public static void main(String[] args) {
		Manager manager = new Manager(); 
		UnderLinePen linePen = new UnderLinePen('x'); //1
		MessageBox mbox = new MessageBox('*'); //1 
		MessageBox sbox = new MessageBox('/'); //1
		manager.register("Emphasized message", linePen);// 2
		manager.register("Warning box",mbox); //2
		manager.register("Diagonal box", sbox);  //2

//Generate
		Product p1 = manager.create("Emphasized message");//3
		p1.use("Hello world");   //4
		Product p2 = manager.create("Warning box"); //3
		p2.use("Hello world");   //4
		Product p3 = manager.create("Diagonal box"); //3
		p3.use("Hello world");   //4
	}
}

Execution result

¥ Hello world ¥
xxxxxxxxxxxxxxx
***************
* Hello world *
***************
///////////////
/ Hello world /
///////////////

Interpretation

1. Set the characters to be drawn on Concrete Product
2. Register Concrete Products in HashMap of Manager
3. Create a clone with Manager.create → Product.createClone returns its own clone
4. Draw with Product.use

Implementation class diagram

--Product is the role of Prototype --MessageBox, UnderLinePen is the role of ConcretePrototype --Manager is the role of Client

Quote

Augmented and revised edition Introduction to design patterns learned in Java language|Hiroshi Yuki|Computer / IT|Kindle Store| Amazon

[6 . Prototype pattern \ | TECHSCORE ](https://www.techscore.com/tech/DesignPattern/Prototype.html/)