Object pooling API.

The org.apache.commons.pool2 package defines a simple interface for a pool of object instances, and a handful of base classes that may be useful when creating pool implementations.

The pool package itself doesn't define a specific object pooling implementation, but rather a contract that implementations may support in order to be fully interchangeable.

The pool package separates the way in which instances are pooled from the way in which they are created, resulting in a pair of interfaces:

{@link org.apache.commons.pool2.ObjectPool ObjectPool}

defines a simple object pooling interface, with methods for borrowing instances from and returning them to the pool.

{@link org.apache.commons.pool2.PooledObjectFactory PooledObjectFactory}

defines lifecycle methods for object instances contained within a pool. By associating a factory with a pool, the pool can create new object instances as needed.

The pool package also provides a keyed pool interface, which pools instances of multiple types, accessed according to an arbitrary key. See {@link org.apache.commons.pool2.KeyedObjectPool KeyedObjectPool} and {@link org.apache.commons.pool2.KeyedPooledObjectFactory KeyedPooledObjectFactory}.