/*idea :跟着"任亮"做练习题 21,异常;
计算圆的面积,通过自定义异常来设计,半径不能为零和负数,采用异常机制处理
一;创建构造器:;
homework家庭作业*/
package cn.tx.homework;
//ValidData有效数据;ValidDataExceotion非法数据异常
public class ValidDataExceotion extends RuntimeException{
//继承父类构造器 Ctrl+O; 用Shift选前5个
public ValidDataExceotion() {
super();
}
public ValidDataExceotion(String message) {
super(message);
}
public ValidDataExceotion(String message, Throwable cause) {
super(message, cause);
}
public ValidDataExceotion(Throwable cause) {
super(cause);
}
protected ValidDataExceotion(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
super(message, cause, enableSuppression, writableStackTrace);
}
}
二:创建方法
package cn.tx.homework;
import java.util.Scanner;
public class Demo {
//计算面积;建立一个方法;getArea获得面积; area面积;
public static double getArea(double r){
//面积初始值
double area = 0;
//抛出异常
if (r<=0) {
throw new ValidDataExceotion(“半径不可以是负或零”);
}
//Math 类包含用于执行基本数学运算的方法,如初等指数、对数、平方根和三角函数。
area = Math.PIrr;
return area;
}
public static void main(String[] args) {
//Scanner键盘输入
Scanner s = new Scanner(System.in);
System.out.println("请输入圆的半径");
int r = s.nextInt();
double area = 0;
try {
//area = getArea(10);抛出异常ctrl+alt+t
area = getArea(r);
System.out.println("圆的面积是:"+area);
} catch (Exception e) {
if (e instanceof ValidDataExceotion){
System.out.println("传递的参数错误.请重新输入");
r= s.nextInt();
area = getArea(r);
System.out.println("圆的面积是:"+area);
}
}
}
}