举个栗子——自定义异常类

自定义异常类举例

• 使用自定义的异常类
• 老师用电脑上课
• 老师发生上课异常
• 上课时电脑发生蓝屏或者冒烟异常

public class Demo {
    public static void main(String[] args) {
        Teacher1 teacher1 = new Teacher1(new Computer());
        try {
            teacher1.work();
        }catch (ClassingException e) {
            e.printStackTrace();
            System.out.println("去修电脑");
        }
    }
}

//创建三个异常类
class ClassingException extends Exception{
    public ClassingException() {}

    public ClassingException(String message) {
        super(message);
    }
}

class LanPingException extends Exception{
    public LanPingException() {
    }

    public LanPingException(String message) {
        super(message);
    }
}

class MaoYanException extends Exception{
    public MaoYanException() {
    }

    public MaoYanException(String message) {
        super(message);
    }
}

class Teacher1 {
    Computer computer;

    public Teacher1(Computer computer) {
        this.computer = computer;
    }
    //老师上课
    public void work() throws ClassingException
    {
        try {
            computer.computerWork();
        } catch (LanPingException  e) {
            e.printStackTrace();
            computer.reset();
        } catch (MaoYanException  e) {
            e.printStackTrace();
            throw new ClassingException("老师无法继续上课");
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}

class Computer{
    //设定当前的状态值:代表要发生的异常   1.蓝屏    2.冒烟
    int status = 2;
    //重启方法
    public void reset(){
        System.out.println("重启电脑");
    }

    //电脑工作
    public void computerWork() throws LanPingException,MaoYanException 
    {
        switch (status) {
        case 1://蓝屏
            throw new LanPingException("电脑蓝屏了");
            //break;
        case 2://冒烟
            throw new MaoYanException("电脑冒烟了");
            //break;
        default:
            break;
        }
    }
}

//在重写的方法中使用异常的注意点:
/*
 * 1.子类的同名方法中声明的异常等级要=<父类的.
 * 2.子类的同名方法中声明的异常可以与父类的不一致,也可以不声明异常.但是此时子类方法不能再抛出异常
 * 3.如果子类同名方法声明了异常,父类必须声明异常.
 */
class BadComputer extends Computer{

    public void computerWork() throws LanPingException, MaoYanException {

    }
}