Final fields state when accessed from subclass

Question

I see a strange behaviour which seems shouldn't happen according to JMM. I have class B which extends class A, a final protected field in A which is initialized in A constructor accessed by class B in its constructor.

But, in very rare cases I get a NPE when accessed in B. Any ideas?

Part of the code:

class AsyncReplicationSourceGroup extends AbstractReplicationSourceGroup{

    public AsyncReplicationSourceGroup(DynamicSourceGroupConfigHolder groupConfig){
        super(groupConfig);
        createReplicationChannels();  
    }

    protected void createReplicationChannels(){
        //...
        specificLogger.finest("created channel");  // this is where the NPE is thrown from
        //...
    }
}

abstract class AbstractReplicationSourceGroup{

    protected final Logger specificLogger;

    public AbstractReplicationSourceGroup(DynamicSourceGroupConfigHolder groupConfigHolder){
        specificLogger = Logger.getLogger(Constants.LOGGER_REPLICATION_GROUP + "." + _groupConfigHolder.getConfig().getName());
        //...
    }

}

Answer 1

It's impossible to tell for sure from the code posted alone, but if you are sure that the logger itself is null, (and you aren't mistakenly seeing a NPE from inside say, specificLogger.finest), then the most likely explanation is that Logger.getLogger is occasionally returning null for some reason.

I don't think the problem is threading because final fields assigned to in a constructor are guaranteed to be visible once the constructed object is visible as long as no references leak inside the constructor.