Proposal: Fully Concurrent ClassLoading

Mandy Chung mandy.chung at
Fri Dec 7 23:46:46 UTC 2012

On 12/5/12 3:59 AM, David Holmes wrote:
> Java 7 introduced support for parallel classloading by adding to each 
> class loader a ConcurrentHashMap, referenced through a new field, 
> parallelLockMap. This contains a mapping from class names to Objects 
> to use as a classloading lock for that class name. This scheme has a 
> number of inefficiencies. To address this we propose for Java 8 the 
> notion of a fully concurrent classloader ...
> This is a fairly simple proposal that I've written up as a blog entry:
It's a good and simple proposal and also handles the backward 
compatibility nicely.

I think having getClassLoadingLock() to return null for a fully 
concurrent loader is a good idea.  In case if any code synchronizes on 
the returned value after migrating to fully concurrent class loader, it 
will catch such usage (it might be very rare)/

I agree with Alan's suggestion - we should consider deprecating 


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