code: static IOException getCauseIfDiskError(IOException ioe) {
      if (ioe.getMessage()!=null && ioe.getMessage().startsWith(DISK_ERROR)) {
        return (IOException)ioe.getCause();
      } else {
        return null;
      }
    }
docs: Get the cause of an I/O exception if caused by a possible disk error
  @param ioe an I/O exception
  @return cause if the I/O exception is caused by a possible disk error;
  null otherwise.