Prototype

🐑 Prototype

Prototype is a creational design pattern that lets you copy existing objects without making your code dependent on their classes.

Applicability

Use the Prototype pattern when a system should be independent of how its products are created, composed, and represented; and

• When the classes to instantiate are specified at run-time, for example, by dynamic loading.
• To avoid building a class hierarchy offactories that parallels the class hierarchy of products.
• When instances of a class can have one of only a few different combinations of state. It may be more convenient to install a corresponding number of prototypes and clone them rather than instantiating the class manually, each time with the appropriate state.

General Structure

• Prototype : declares an interface for cloning itself.
• ConcretePrototype : implements an operation for cloning itself.
• Client : creates a new object by asking a prototype to clone itself.

Example

Remember Dolly? The sheep that was cloned! Lets not get into the details but the key point here is that it is all about cloning.

In plain words : Create an object based on an existing object through cloning.

In Java, the prototype pattern is recommended to be implemented as follows. First, create an interface with a method for cloning objects. In this example, Prototype interface accomplishes this with its copy method.

The code source : source folder

  public static void main(String []args){

    CloneFactory animalMaker = new CloneFactory();

    //Create object type sheep and dog
    Sheep sally = new Sheep();
    Dog max = new Dog();

    //Clone sheep and dog instance
    Sheep clonedSheep = (Sheep) animalMake.getClone(sally);
    Dog clonedDog = (Dog) animalMake.getClone(max);

    System.out.println("Sally hashCode:- "+ sally.hashCode());
    System.out.println("SallyClone hashCode:- "+ clonedSheep.hashCode());

    System.out.println("\nMax hashCode:- "+ max.hashCode());
    System.out.println("MaxClone hashCode:- "+ clonedDog.hashCode());

  }

Output :

    Sally hashCode:- 1435741095
    SallyClone hashCode:- 1981243562

    Max hashCode:- 1550089733
    MaxClone hashCode:- 1346782756