Removing synchronization on metadata?

[Martin Desruisseaux]

Hello all

A while ago, we talked about metadata synchronization on this mailing 
list. If one take a look at any metadata class in 
"org.apache.sis.metadata.iso", we can see that all getter and setter 
methods are declared synchronized. In my understanding, it doesn't 
consume any space in the "*.class" files since the "synchronized" 
modifier only set a bit in the bytecodes (I verified that removing 
"synchronized" doesn't make any difference on the metadata *.class files).

Nevertheless we mentioned the possibility to remove synchronization 
because it seems rarely needed in practice, since the most common 
pattern is to build a metadata in a single thread and keep it 
unmodifiable after construction. Furthermore, if someone really wants 
synchronization, he will probably needs something more elaborated (e.g. 
a lock on a whole metadata tree instead than on the instance of a 
particular property). On the other hand, removing synchronization reduce 
safety if a user read and write concurrently a metadata by accident.

So I'm still not sure what is the best option. I'm heading toward 
removing synchronization, but if anyone think that we should keep them 
please let me know.

    Martin