java-自定义异常操作

/*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。问题通过异常来表示。现有对这个程序进行基本设计。*///自定义异常class NoValueException extends RuntimeException{NoValueException(String message){super(message);}}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("出现负数了");   //注意newelse{this.len=len;this.wid=wid;}}public void getArea(){System.out.println(len*wid);}}class Circle implements Shape{private int redius;public static final double PI = 3.14;Circle(int redius){if(redius<=0)throw new NoValueException("出现负数了");this.redius=redius;}public void getArea(){System.out.println(redius*redius*PI);}}class ExceptionTest{public static void main(String[] args) {//try//{Rec r = new Rec(3,4);r.getArea();//}//catch (NoValueException e)//{//System.out.println(e.toString());//}Circle c = new Circle(-3);c.getArea();}}