This bug was found by St.Petersburg Java SQE team (by Stanislav Avzan).

The Java Language specification (Version 1.0 - August 1, 1996) does not describe case of negative n of java.io.InputStream.skip(n) method.

Specification says (see item 22.3.4):
"22.3.4 public long skip(long n) throws IOException

The general contract of skip is that it makes an attempt to skip over n bytes
of data from the input stream, discarding the skipped bytes. However, it may
skip over some smaller number of bytes, possibly zero. This may result from
any of a number of conditions; reaching end of file before n bytes have
been skipped is only one possibility. The actual number of bytes skipped is
returned."

This statement does not describe behaviour of this method in case of negative n.