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Creational Patterns  «Prev 

Prototype Pattern in Java

In the prototype pattern, a new object is created by cloning an existing object. In Java, the clone() method is an implementation of this design pattern. The prototype pattern can be a useful way of creating copies of objects. One example of how this can be useful is if an original object is created with a resource such as a data stream that may not be available at the time that a clone of the object is needed.
Another example is if the original object creation involves a significant time commitment, such as reading data from a database.
An added benefit of the prototype pattern is that it can reduce class proliferation in a project by avoiding factory proliferation.
We can implement our own prototype pattern. To do so, we'll create a Prototype interface that features a doClone() method.

package com.java.creational.prototype;

public interface Prototype {
  public Prototype doClone();
}

The Person class implements the doClone() method. This method creates a new Person object and clones the name field. It returns the newly cloned Person object.

package com.java.creational.prototype;

public class Person implements Prototype {
	String name;
	public Person(String name) {
		this.name = name;
	}
	@Override
	public Prototype doClone() {
		return new Person(name);
	}
	public String toString() {
		return "This person is named " + name;
	}
}
>
The Cat class also implements the doClone() method. This method creates a new Cat object and clones the sound field. The cloned Cat object is returned.

package com.java.creational.prototype;

public class Cat implements Prototype {
 String sound;
 public Cat(String sound) {
  this.sound = sound;
 }
 @Override
 public Prototype doClone() {
  return new Cat(sound);
 }
 public String toString() {
  return "This cat says " + sound;
 }
}

The Demo class creates a Person object and then clones it to a second Person object.
It then creates a Cat object and clones it to a second Cat object.
package com.java.creational.prototype;

public class PrototypeExample {
 public static void main(String[] args) {
  Person person1 = new Person("Glenn");
  System.out.println("person 1:" + person1);
  Person person2 = (Person) person1.doClone();
  System.out.println("person 2:" + person2);
  Cat cat1 = new Cat("Meow");
  System.out.println("cat 1:" + cat1);
  Cat cat2 = (Cat) cat1.doClone();
  System.out.println("cat 2:" + cat2);
 }
}
Program output:
person 1:This person is named Glenn
person 2:This person is named Glenn
cat 1:This cat says Meow
cat 2:This cat says Meow