Throwing User defined Exception

public class MyException extends Exception
    {
     String msg = "";
     int marks;
     public MyException()
         {
     }
     public MyException(String str)
         {
         super(str);
     }
     public String toString()
         {
         if(marks <= 40)
         msg = "You have failed";
         if(marks > 40)
         msg = "You have Passed";
        
         return msg;
        
     }
}


public class test
    {
     public static void main(String args[])
         {
         test t = new test();
         t.dd();
     }
     public void dd()
         {
         try
             {
             int i=0;
             if( i < 40)
             throw new MyException();
         }
         catch(MyException ee1)
             {
             System.out.println("my ex"+ee1);
         }
     }
}