Prototype design pattern — Java

Definition of Prototype pattern

The prototype pattern is a creational design pattern in software development. It is used when the type of objects to create is determined by a prototypical instance, which is cloned to produce new objects.

Where to use the Prototype pattern

If the cost for creating a new object is expensive and costs resources.

UML example of the Prototype pattern

Implementation of the builder pattern

First we need to create our prototype class

	package main.prototype;
	public interface Prototype {
	public Prototype getClone();
	}

view raw Prototype.java hosted with ❤ by GitHub

The getClone() *method will be implemented in the class that will implement the prototype to return a new object of the same class.
In the next example we will create a Human and then implement the method to clone him.

	package main.prototype;
	public class Human implements Prototype{
	private String name;
	private String lastName;
	private int age;
	public Human(){
	System.out.println(" Human description ");
	System.out.println("---------------------------------");
	System.out.println("Name"+"\t"+"Last Name"+"\t"+"Age");
	}
	public Human(String name, String lastName, int age) {
	this();
	this.name = name;
	this.lastName = lastName;
	this.age = age;
	showHuman();
	}
	private void showHuman(){
	System.out.println(name+"\t"+lastName+"\t"+age);
	}
	@Override
	public Prototype getClone() {
	return new Human(name, lastName, age);
	}
	}

view raw HumanPrototype.java hosted with ❤ by GitHub

As you can read, the *getClone() will return me another Human with the same name, last name and age to the one created before.

Exemple :

The following code will give me the following output

	package main.prototype;
	public class HumanPrototypeMain extends Human {
	public static void main(String[] args) {
	Human human1 = new Human("Erwan", "Le Tutour", 30);
	Human human2 = (Human) human1.getClone();
	}
	}

view raw HumanPrototypeMain.java hosted with ❤ by GitHub

Human description
---------------------------------
Name Last Name Age
Erwan Le Tutour 30
Human description
---------------------------------
Name Last Name Age
Erwan Le Tutour 30

As you can see above, my human2 has the same properties values as my human1, but they will only be equals if I implement the *equals() *method to do so.