2906. Design Pattern - Prototype
Prototype Pattern

Creational Pattern: Prototype Pattern.

1. Prototype Pattern

Prototype pattern refers to creating duplicate object while keeping performance in mind. Specify the kinds of objects to create using a prototypical instance, and create new objects by copying this prototype.

2. Example of Implementation

2.1 Base Class

public abstract class Shape implements Cloneable { private String id; protected String type; abstract void draw(); public String getType(){ return type; } public String getId() { return id; } public void setId(String id) { this.id = id; } public Object clone() { Object clone = null; try { clone = super.clone(); } catch (CloneNotSupportedException e) { e.printStackTrace(); } return clone; } }

2.2 Classes

public class Circle extends Shape { public Circle(){ type = "Circle"; } @Override public void draw() { System.out.println("Shape: Circle"); } } public class Rectangle extends Shape { public Rectangle(){ type = "Rectangle"; } @Override public void draw() { System.out.println("Shape: Rectangle"); } } public class Square extends Shape { public Square(){ type = "Square"; } @Override public void draw() { System.out.println("Shape: Square"); } }

2.3 Usage

public class ShapeCache { private static Map<String, Shape> mapShape = new HashMap<>(); public static Shape getShape(String shapeId) { Shape cachedShape = mapShape.get(shapeId); return (Shape) cachedShape.clone(); } public static void loadCache() { Circle circle = new Circle(); circle.setId("1"); mapShape.put(circle.getId(), circle); Square square = new Square(); square.setId("2"); mapShape.put(square.getId(), square); Rectangle rectangle = new Rectangle(); rectangle.setId("3"); mapShape.put(rectangle.getId(), rectangle); } }

Get new object from cache without directly creating new instance.

public class Client { public void run() { ShapeCache.loadCache(); Shape clonedShape = (Shape) ShapeCache.getShape("1"); System.out.println("Shape : " + clonedShape.getType()); Shape clonedShape2 = (Shape) ShapeCache.getShape("2"); System.out.println("Shape : " + clonedShape2.getType()); Shape clonedShape3 = (Shape) ShapeCache.getShape("3"); System.out.println("Shape : " + clonedShape3.getType()); } }

Output.

Shape : Circle Shape : Square Shape : Rectangle

3. Source Files

4. References