异常练习（自定义异常）

练习一：

package Exception;
/**
 * 计算一个圆和长方形的面积？
 * 注意：面积不能为0和负数。请用异常来描述；
 * @author asus1
 *
 */
//自定义一个异常
class NovalueException extends RuntimeException{
    NovalueException(String mssage){
        super(mssage);
    }
}
public class ExceptionDemo3 {

    public static void main(String[] args) {
        try {
            ricImpl ri = new ricImpl(5,2);
            double riArea = ri.getArea();
            System.out.println(riArea);
            
            CirlcImpl ci = new CirlcImpl(-5);
            double ciArea = ci.getArea();
            System.out.println(ciArea);
            
        } catch (NovalueException e) {
            System.out.println(e.toString());
        }
        
    }

}

interface Shape {
    double getArea();
}

class ricImpl implements Shape{
    private double width;
    private double height;
    ricImpl(double width,double height) throws NovalueException{
        if(width <=0 || height<=0){
            throw new NovalueException("非法数据");
        };
        this.width = width;
        this.height = height;
    }
    public double getArea(){
        return width*height;
    }
}
class CirlcImpl implements Shape{
    private double radius;
    public static final double PI = 3.14;
    CirlcImpl(double radius) throws NovalueException{
        if(radius <=0){
            throw new NovalueException("圆--非法数据");
        }
        this.radius = radius;
    }
    public double getArea(){
        return radius*radius*PI;
    }
}

练习二：

package Exception;
/**
 * 老师讲课
 * 问题：1.电脑蓝屏了
 *         2.电脑冒烟了
 * 需求：解决以上两异常
 * @author asus1
 *
 */
class lanpinException extends Exception{  //蓝屏异常
    lanpinException(String mssage){
        super(mssage);
    }
}
class maoyanException extends Exception{  //冒烟异常
    maoyanException(String mssage2){
        super(mssage2);
    }
}
public class Exception_lianxi {

    public static void main(String[] args) {
        Teacher t = new Teacher("童");
        t.prelect();
        System.out.println("讲课了");
    }

}
class Teacher{
    private String name;
    public Teacher(String name) {
        super();
        this.name = name;
    }
    public void prelect(){
        Complate co = new Complate();
        try {//正常
            co.run();
        } catch (lanpinException e) {  //蓝屏异常抛出
            //解决蓝屏异常的代码
            System.out.println(e.getMessage());
            co.reset();                
        }catch (maoyanException e) {  //冒烟异常抛出
            //解决冒烟异常的代码
            System.out.println(e.getMessage());
            gotolianxi lianxi = new gotolianxi();
            //lianxi.toString();
        }
        
    }
}
class gotolianxi{
    public gotolianxi(){
        System.out.println("去练习");
    }
}
class Complate{
    private int state = 3;  //1- 正常 ; 2- 蓝屏;  3- 冒烟;
    
    public void run() throws lanpinException,maoyanException{
        if(state == 1){
            System.out.println("runing!!");
        }
        if(state == 2){
            throw new lanpinException("电脑蓝屏了-");//抛出编译时检测的异常 需要在方法外声明定义这个异常
        }
        if(state == 3){
            throw new maoyanException("电脑冒烟了-");
        }
    }
    public void reset(){
        System.out.println("电脑重启ing");
    }
}