Question

I wanted to use the skip method of FilterInputStream class which should skip over the required number of bytes from the stream.
But the documentation for the skip method says
http://docs.oracle.com/javase/1.4.2/docs/api/java/io/FilterInputStream.html#skip(long)

Skips over and discards n bytes of data from the input stream. The skip method may, for a variety of reasons, end up skipping over some
smaller number of bytes, possibly 0. The actual number of bytes
skipped is returned.

Is it really safe to use then the skip method for the purpose of seeking to a particular position?

Answer 1

I also find this API a little problematic. It leaves too much freedom to the specific implementations:

1) It’s not clear what happens in case of end of stream

2) It’s not clear whether when the stream is non-empty, repeatedly calling skip will eventually return a positive number or not.

Assuming that you know that n isn’t beyond the end of stream, and assuming that (2) holds, then the following code may be helpful:

public static void skipSecure(InputStream is, long n) throws IOException {
    while (n >= 0) {
        long skipped = is.skip(n);
        n -= skipped;
    }
}