棋子

  简单工厂模式优点: 开-闭原则：对扩展开放，对修改关闭
  设计思路讲解:1、声明一个接口,并定义方法.
          2、添加所要实现的类
          3、实例所用的类.
  代码实现:
public   interface Shape
{
    public void draw();
    public double area();
}
public   class Circle implement Shape
{
    private double radio;
    protect Circle(){
          radio=10;
    }
    public void draw(){
        System.out.println(“画圆”);
    }
    public double area(){
          return 3.14159*radio*radio
    }
}
public   class Square implement Shape
{
    private double length;
    protect Square (){
        length =10;
    }
    public void draw(){
        System.out.println(“画正方形”);
    }
    public double area(){
          return length * length
    }
}
public class ShapeFactory{
    public static Shape createShape (String which){
        Shape shape=null;
        if(which.equals(“circle”)) shape=new Circle();
        if(which.equals(“square”)) shape=new Square();
     
        if(shape==null) System.out.println(“bad Shape”);
        return shape;
    }
}
public class Client {
    public static void main(String[] args){
        Shape shape=ShapeFactory. createShape(“circle”);
        shape.draw();
        double area=shape.area();
  }
}
   
      UML分析: