GetMessage() displays null for EXCEPTIONS.Please guide

Question

I have created my own Exception class called InvalidAccountException which extends InternalException.
My code throws an exception if an invalid account in set.
Thats fine.I get the exception shown.
But when I say te.getMessage() in the catch clause,is displays null
Any idea why?
class Customer{
public static void main(String[] args) {
     AccountInfo acInfo = new AccountInfo();
     acInfo.setAccount(100);
     // Create customer.
     VirtualPerson cust = new VirtualPerson();
     try {
           cust.readAccount(acInfo);
         }catch(InvalidAccountException te){
              System.out.println(te);                             // Works
              //System.out.println(te.getMessage().toString());   // displays null.Why?
         }catch(InternalException ie){
             //System.out.println(te.getMessage().toString());    // displays null
}

Answer 1

Last, but only because the first post didn't show. <_<Bah, excuses ;)