When synchronizing methods or fields between an interface 
and an implementing class, Netbeans adds the members to 
the implementing class in alphabetic order, not the order 
they are defined in the interface. Also, any methods added 
later are added at the end of the file.

As a result, the source file becomes jumbled and related 
methods are spread apart, often violating other code 
conventions (eg put private methods after public). This 
severely limits the usefulness of the synchronization 
feature.

I reported this about 2 years ago, but I cannot find  the 
original issue.