How to protect dynamic lookup content when it is changing?

Boris Heithecker wrote:
> 
> B: no listeners, you just want the lookup to never be empty -> you could reverse the order of invocation (instanceContent.add(newKey) before instanceContent.remove(oldKey))
> 


yes. that should do the work. so simple. thanks :)


you said that getLookup is thread safe so i wonder if i lock instancontent in setNewKey() like this:



Code:

public void setNewKey(SomeKey key) { 

        Collection<? extends SomeKey> lookupAll = getLookup().lookupAll(SomeKey.class); 

        synchronized(instanceContent)
            for (SomeKey item : lookupAll) { 
                 instanceContent.remove(item); 
            } 

//if getLookup.lookup(SomeKey.class) is invoked by another thread at this point, will it be blocked untill end of this synchronized block?
         }
 

        instanceContent.add(key); 
    }