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;
   }
}

import java.util.Hashtable;

class Square extends Shape {

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

    @Override
    public void draw() {
        System.out.println("draw square");
    }
}

class Circle extends Shape {

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

    @Override
    public void draw() {
        System.out.println("draw circle");
    }
}

class ShapeCache {

    private static final Hashtable<String, Shape> shapeMap
            = new Hashtable<>();

    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);
    }
}

public class PrototypePatternDemo {
    public static void main(String[] args) {
        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());
    }
}