public long skip(long bytesToSkip)
 throws IOException

The argument to the skip() method is the number of bytes to skip.
The return value is the number of bytes actually skipped, which may be less than bytesToSkip.

-1

is returned if the end-of-stream is encountered.
The skip() method takes and returns longs so that it can handle very long input streams, particularly those associated with large files.

public long skip(long bytesToSkip) throws IOException

The argument to skip() is the number of bytes to skip. The return value is the number of bytes actually skipped, which may be less than bytesToSkip. -1 is returned if the end of stream is encountered. Both the argument and return value are longs, allowing skip() to handle extremely long input streams. Skipping is often faster than reading and discarding the data you don't want. For example, when an input stream is attached to a file, skipping bytes just requires that an integer called the file pointer be changed, whereas reading involves copying bytes from the disk into memory. For example, to skip the next 80 bytes of the input stream in:

try {
 long bytesSkipped = 0;
 long bytesToSkip = 80;
 while (bytesSkipped < bytesToSkip) {
  long n = in.skip(bytesToSkip - bytesSkipped);
  if (n == -1) break;
    bytesSkipped += n;
  }
}
catch (IOException e) {
  System.err.println(e);
}