手动抛出

package exer;
//手动的抛出一个异常的格式
public class MyException extends Exception{
    static final long serialVersionUTD = -703489545;
    public MyException(){

    }
    public MyException(String msg){
        super(msg);
    }
}

package exer;

public class TestStudent {
    public static void main(String[] args){
        Student s=new Student();
        try{
            s.regist(-12);
        }catch(MyException e){
            System.out.println(e.getMessage());
        }
        System.out.println(s);
    }
}

class Student{
    private int id;
    public void regist(int id) throws MyException{
        if(id>0)
            this.id=id;
        else {
            throw new MyException("输入的学号有误");
        }
    }
    public String toString() {
        return "Student [id=" + id + "]";
    }

}