Performs any initialization of the subclass of
FileBasedReader that involves IO
operations. Will only be invoked once and before that invocation the base class will seek the
channel to the source's starting offset.
Provided
ReadableByteChannel is for the file represented by the source of this
reader. Subclass may use the
channel to build a higher level IO abstraction, e.g., a
BufferedReader or an XML parser.
If the corresponding source is for a subrange of a file,
channel is guaranteed to
be an instance of the type
SeekableByteChannel.
After this method is invoked the base class will not be reading data from the channel or
adjusting the position of the channel. But the base class is responsible for properly closing
the channel.