This class is a FilterInputStream descendant that reads from an underlying InputStream
up to a defined number of bytes or the end of the underlying stream. Closing this InputStream
will not result in the underlying InputStream to be closed, too.
This InputStream can be used to read chunks from a larger file of which the length is
known in advance.
Creates a new SubInputStream.
Parameters: in - the InputStream to read from Parameters: maxLen - the maximum number of bytes to read from the underlying InputStream untilthe end-of-file is signalled.