| A nexus for I/O operations.
A channel represents an open connection to an entity such as a hardware
device, a file, a network socket, or a program component that is capable of
performing one or more distinct I/O operations, for example reading or
writing.
A channel is either open or closed. A channel is open upon creation,
and once closed it remains closed. Once a channel is closed, any attempt to
invoke an I/O operation upon it will cause a {@link ClosedChannelException}
to be thrown. Whether or not a channel is open may be tested by invoking
its {@link #isOpen isOpen} method.
Channels are, in general, intended to be safe for multithreaded access
as described in the specifications of the interfaces and classes that extend
and implement this interface. | 