Error building wicket-6.19.0 from src

[Chris Colman]

I get the following error when I try to compile the 6.19.0 source code:
 
 [ERROR] 7014: org.apache.wicket.feedback.FeedbackCollector: Method
'public java.util.List collect()' is now final
[ERROR] 7014: org.apache.wicket.feedback.FeedbackCollector: Method
'public java.util.List collect(org.apache.wicket.feed
back.IFeedbackMessageFilter)' is now final
[ERROR] 7014: org.apache.wicket.feedback.FeedbackCollector: Method
'public org.apache.wicket.feedback.FeedbackCollector
setIncludeSession(boolean)' is now final
[ERROR] 7014: org.apache.wicket.feedback.FeedbackCollector: Method
'public org.apache.wicket.feedback.FeedbackCollector
setRecursive(boolean)' is now final
 
Any idea what could be causing this?
 
Regards,
Chris