Base implementation class for selectable channels.
This class defines methods that handle the mechanics of channel
registration, deregistration, and closing. It maintains the current
blocking mode of this channel as well as its current set of selection keys.
It performs all of the synchronization required to implement the java.nio.channels.SelectableChannel specification. Implementations of the
abstract protected methods defined in this class need not synchronize
against other threads that might be engaged in the same operations.
extends