Java 原型模式

Java設(shè)計(jì)模式 - 原型模式

原型模式是創(chuàng)建模式之一。

原型模式有助于創(chuàng)建具有更好性能的重復(fù)對(duì)象。

在原型模式中，將返回一個(gè)現(xiàn)有對(duì)象的克隆，而不是創(chuàng)建新的對(duì)象。

我們使用原型設(shè)計(jì)模式，如果創(chuàng)建一個(gè)新對(duì)象的成本是昂貴和資源密集型。

例子

以下代碼顯示如何使用Prototype Pattern創(chuàng)建對(duì)象。

首先它創(chuàng)建一個(gè)Shape抽象類，實(shí)現(xiàn)Cloneable接口。

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;
   }
}

然后它創(chuàng)建三個(gè)具體的類擴(kuò)展Shape類。

class Rectangle extends Shape {

   public Rectangle(){
     type = "Rectangle";
   }

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

   public Square(){
     type = "Square";
   }

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

   public Circle(){
     type = "Circle";
   }

   @Override
   public void draw() {
      System.out.println("Inside Circle::draw() method.");
   }
}

之后，它創(chuàng)建一個(gè)ShapeProtoType類來(lái)返回形狀的原型。

class ShapeProtoType{
   private static Hashtable<String, Shape> shapeMap 
      = new Hashtable<String, Shape>();

   public static Shape getShape(String shapeId) {
      Shape cachedShape = shapeMap.get(shapeId);
      return (Shape) cachedShape.clone();
   }
   public static void loadCache() {
      Circle circle = new Circle();
      circle.setId("1");
      shapeMap.put(circle.getId(),circle);

      Square square = new Square();
      square.setId("2");
      shapeMap.put(square.getId(),square);

      Rectangle rectangle = new Rectangle();
      rectangle.setId("3");
      shapeMap.put(rectangle.getId(),rectangle);
   }
}
public class Main{
   public static void main(String[] args) {
      ShapeProtoType.loadCache();

      Shape clonedShape = (Shape) ShapeProtoType.getShape("1");
      System.out.println("Shape : " + clonedShape.getType());    

      Shape clonedShape2 = (Shape) ShapeProtoType.getShape("2");
      System.out.println("Shape : " + clonedShape2.getType());    

      Shape clonedShape3 = (Shape) ShapeProtoType.getShape("3");
      System.out.println("Shape : " + clonedShape3.getType());    
   }
}

上面的代碼生成以下結(jié)果。