fd = 0;
  protected void implCloseChannel() throws IOException  {    if (address != 0)      {        nio_unmmap_file (fd, address, (int) length);        address = 0;      }    // FIXME    fd = 0;    if (file_obj instanceof RandomAccessFile)      {        RandomAccessFile o = (RandomAccessFile) file_obj;        o.close();      }    else if (file_obj instanceof FileInputStream)      {        FileInputStream o = (FileInputStream) file_obj;        o.close();      }    else if (file_obj instanceof FileOutputStream)      {        FileOutputStream o = (FileOutputStream) file_obj;        o.close();      }  }