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
to be thrown. Whether or not a channel is open may be tested by invoking
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.