Prototype Pattern

Prototype Pattern에 대해 설명하는 페이지입니다.

Posted Dec 14, 2023

By HyunJinNo

Tags

Design Pattern, Java

1. Introduction

• Purpose
  • Create objects based upon a template of an existing objects through cloning.
• Use When
  • Composition, creation, and representation of objects should be decoupled from a system
  • Classes to be created are specified at runtime.
  • Objects or object structures are required that are identical or closely resemble other existing objects or object structures.
  • The initial creation of each object is an expensive operation.
  • When to avoid building a class hierarchy of factories that parallels the class hierarchy of products

2. Characteristics

• Advantage
  • Hides concrete product classes from clients
  • Decouples the clients from the creational process
• Prototypes can be supplied and changed at runtime
• The client asks the prototype to clone itself for a new object of the prototype.
• It provides great flexibility in configuring and changing a program at runtime
  • Adding and removing products at run-time
  • Reduced subclassing
  • Configuring an application with classes dynamically
    • Loading the classes dynamically

3. Participants

• Prototype
  • Defines the interface (an operation) of cloning itself.
• ConcreteProducts
  • Concrete objects that can clone themselves.
• Client
  • Obtain more objects by asking them to clone themselves.

4. How to Use (Example)

• Java's Cloneable

  java

  1class Stack implements Cloneable {
  2    private final int maxSize;
  3    private int top;
  4    private Object[] store;
  5
  6    public Stack (int size) {
  7        maxSize = size;
  8        store = new Object[size];
  9        top = -1;
  10    }
  11
  12    public Object clone() throws CloneNotSupportedException {
  13        Stack result;
  14        try {
  15            result = (Stack) super.clone();
  16            result.store = (Object[]) store.clone();
  17            return result;
  18        } catch (CloneNotSupportedException e) {
  19            return null;
  20        }
  21    }
  22}