day10-04-面向对象(异常-练习)

需求有一个圆形和长方形都可以获取面积。
对于面积如果出现非法的数值，视为是获取面积出现问题，问题通过异常来处理
现在对这个程序进行基本的设计
看正常流程代码try，看异常流程代码catch

class NoValueException extends RuntimeException
{
    NoValueException(String msg)
    {
        super(msg);
    }
}
interface Shape
{
     void getArea();
}
class Rec implements Shape
{
    private int len,wid;
    Rec(int len,int wid) //throws NoValueException
    {
        if(len<=0||wid<=0)
            throw new NoValueException("非法值");
        this.len = len;
        this.wid = wid;
    }
    public void getArea()
    {
        System.out.println(len*wid);
    }
}
class Circle implements Shape
{
    private int radius;
    public static final double PI= 3.14;
    Circle(int radius)
    {
        if(radius<=0)
            throw new NoValueException("非法值");
        this.radius = radius;
    }
    public void getArea()
    {
        System.out.println(radius*radius*PI);
    }
}

class ExceptionTest1
{
    public static void main(String[] args)
    {   
        Rec r = new Rec(3,4);
        r.getArea();
        
        Circle c = new Circle(-8);
        c.getArea();            
    }
}