设计模式-原型模式

        原型模式是一种创建型设计模式，它用于创建重复的对象，同时又能保证性能。这种类型的设计模式是基于一个原型实例，通过复制（克隆）自身来创建新的对象。

        以下是一个简单的 Java 版本的原型模式的示例：

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;
    }
}
 
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.");
    }
}
 
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() {
        Rectangle rectangle = new Rectangle();
        rectangle.setId("1");
        shapeMap.put(rectangle.getId(), rectangle);
 
        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());
    }
}

        在这个示例中，Shape 是一个实现了 Cloneable 接口的抽象类，Rectangle 和 Square 是 Shape 的具体子类。ShapeCache 类负责存储和克隆原型对象。当需要一个新的 Shape 对象时，可以通过 ShapeCache.getShape 方法获取，这个方法会返回一个克隆的对象，而不是创建一个新的对象。