Enhancement :Allow to set the concurrency level in order to reduce memory about cqengine HOT 6 CLOSED

This is a good suggestion, thanks. And fairly easy to implement.

I'll look into adding some proper support as suggested over the next few days. 

However in the meantime, there is a way to achieve this in the current release, 
even though it's a bit awkward. (I guess you might have done this already...)

You can subclass HashIndex as (say) CustomHashIndex, and override the 
getIndexMap() method. That method should return the same ConcurrentMap every 
time it's called, but you can construct the map with concurrency/load factor 
however you like. Your effectively custom index would then be usable with 
CQEngine as normal.

Expect less awkward support for this in the next few days, in the built-in 
HashIndex and others. Hopefully I'll get time to package this as a 1.0.1 
release at the weekend.

EDIT: actually subclassing alone won't be enough. The current code access the 
map field directly. Grrr. Theoretically for [unvalidated] performance reasons. 
So the temporary workaround might be to copy and paste the code into a 
subclass. ...yes better support for this is definitely required.

Thanks, looking forward to the 1.0.1.

Changes in trunk, will prepare 1.0.1 release over the next few days.

Done.

HashIndex, NavigableIndex and CompoundIndex now optionally accept Factories to 
customize the construction of maps and sets which those indexes use internally.

Example of new methods added to HashIndex:

public static <A,O> HashIndex<A,O> onAttribute(
    Factory<ConcurrentMap<A,StoredResultSet<O>>> indexMapFactory,
    Factory<StoredResultSet<O>> valueSetFactory,
    Attribute<O,A> attribute)

Release 1.0.1 is queued for sync with maven central.