Getting Exception on UseDefinedException sample program - Please help me how to resolve

class UseDefinedException extends Exception{
   String msg = "";
  int marks;
   public UseDefinedException() ){
 }
   public UseDefinedException(String str){
   super(str);
 }
  public String toString(){
   if marks <= 50)
   msg = "You have failed";  

  if marks > 50) 

   msg = "You have Passed"; 
   return msg;
}
}
  public class test{
  public static void main(String args[]){
  test t = new test();
   t.mm();
}
  public void mm(){
  try{
   int i=0;

  if( i < 50) 
  throw new MyException();

}
   catch(MyException ee1){
  System.out.println("my ex"+ee1);
}
}
}

Hi,

I tried above code but getting Exception : MyException cannot be resolved to a type

at Interface.test1.me(test1.java:41)
at Interface.test1.main(test1.java:34)

what is MyException and how it called ..please explain ..?