Object pooling in Java

Quite often, we may have to use object pooling to conserve resources and increase performance.
I came across some pretty good abstract components that can be used to develop a object pooling mechanism.

Check out the followling link to see all the classes that are available for use:
http://jakarta.apache.org/commons/pool/

An interesting aspect of the package was the clear separation of object creation from the way the objects are pooled. There is a PoolableObjectFactory interface that provides a generic interface for managing the lifecycle of a pooled instance.

By contract, when an ObjectPool delegates to a PoolableObjectFactory : -

makeObject is called whenever a new instance is needed.
activateObject is invoked on every instance before it is returned from the pool.
passivateObject is invoked on every instance when it is returned to the pool.
destroyObject is invoked on every instance when it is being "dropped" from the pool (whether due to the response from validateObject, or for reasons specific to the pool implementation.)
validateObject is invoked in an implementation-specific fashion to determine if an instance is still valid to be returned by the pool. It will only be invoked on an "activated" instance.