Since Java mode finally got some improvements recently, maybe someone can solve this too. In Java, enumerations can implement interfaces. However, CC-mode doesn't handle that well. Compare this indentation, for example:

public enum X
{
    A,
    B;
}

public enum X implements Y
{
    A,
        B;
}

Fontification of 'A' and 'B' also changes when I add 'implements' keyword.

Paul