Is it possible to extend Java Enums?

Here's what I am looking to accomplish, I have a class that has an enum of some values and I want to subclass that and add more values to the enum. This is a bad example, but:

public class Digits
{
 public enum Digit
 {
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9
 }
}

public class HexDigits extends Digits
{
 public enum Digit
 {
  A, B, C, D, E, F
 }
}

so that HexDigits.Digit contains all Hex Digits. Is that possible?