A DESCRIPTION OF THE REQUEST :
Change:

public static Container getAncestorOfClass(Class<?>, Component)

  To:

public static <T extends Container> T getAncestorOfClass(Class<T>, Component)

JUSTIFICATION :
This would save the developer a cast for each call. This is a convenience utility class and therrefore should be as convenient as possible.

There is a possibility that the newly proposed signature would break some older code if they passed objects that were not Containers (the method never checked for class type represented by the class instance). If that is a realistic concern, then I recommend producing a properly generic version of getAncestorOfClass with a different name and deprecating the current one.