return lock(nfd.getNativeFD(), pos, len, shared, wait);
return VmChannel.lock(nfd.getNativeFD(), pos, len, shared, wait);
  public boolean lock(long pos, long len, boolean shared, boolean wait)    throws IOException  {    if (kind != Kind.FILE)      throw new IOException("not a file");    return lock(nfd.getNativeFD(), pos, len, shared, wait);  }