在这种情况下，原型模式的好处是什么？(what is the benefit of prototype pattern in this case)

 我看到一些代码以这种方式定义了原型模式： 
 
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;
   }
}
 
 扩展上述类的两个具体类： 
 
public class Rectangle extends Shape {

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

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

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

   @Override
   public void draw() {
      System.out.println("Inside Square::draw() method.");
   }
}
 
 创建一个类以从数据库获取具体类并将它们存储在Hashtable中： 
 
public class ShapeCache {

   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() {

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

      Rectangle rectangle = new Rectangle();
      rectangle.setId("3");
      shapeMap.put(rectangle.getId(), rectangle);
   }
}
 
 我的问题是getShape方法这两个实现之间的区别和好处： 
 
 实施1： 
 
  public static Shape getShape(String shapeId) {
      Shape cachedShape = shapeMap.get(shapeId);
      return (Shape) cachedShape.clone();
   }
 
 并且： 实施2： 
 
 public static Shape getShape(String shapeId) {
      Shape cachedShape = shapeMap.get(shapeId);
      // return (Shape) cachedShape.clone();
     return  cachedShape ;
   }
 
 我尝试了这两种实现，并且他们工作得很好，只是我想知道如果使用第一个实现的好处 

I saw some code defines the prototype pattern in this way :
 
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;
   }
}
 
Two concrete classes extending the above class : 
 
public class Rectangle extends Shape {

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

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

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

   @Override
   public void draw() {
      System.out.println("Inside Square::draw() method.");
   }
}
 
Create a class to get concrete classes from database and store them in a Hashtable : 
 
public class ShapeCache {

   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() {

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

      Rectangle rectangle = new Rectangle();
      rectangle.setId("3");
      shapeMap.put(rectangle.getId(), rectangle);
   }
}
 
My question is in the getShape method what is the difference and benefit between these two implementations : 
 
Implementation 1 : 
 
  public static Shape getShape(String shapeId) {
      Shape cachedShape = shapeMap.get(shapeId);
      return (Shape) cachedShape.clone();
   }
 
And : Implementation 2 :
 
 public static Shape getShape(String shapeId) {
      Shape cachedShape = shapeMap.get(shapeId);
      // return (Shape) cachedShape.clone();
     return  cachedShape ;
   }
 
I tried the two implementations and they work well just I want to know the benefit if I use the first Implementation

原文：https://stackoverflow.com/questions/40419778