Clears the specified pool, removing all pooled instances corresponding to the given <code>key</code> (optional operation).
@param key the key to clear
@throws UnsupportedOperationException when this implementation doesn't support the operation
@throws Exception if the key cannot be cleared
See Implementation
Clears the specified pool, removing all pooled instances corresponding to the given <code>key</code> (optional operation).
@param key the key to clear
@throws UnsupportedOperationException when this implementation doesn't support the operation
@throws Exception if the key cannot be cleared