public void remove(String key) throws MqttPersistenceException {
  checkIsOpen();
  File file=new File(clientDir,key + MESSAGE_FILE_EXTENSION);
  if (file.exists()) {
    file.delete();
  }
}

public void remove ( String key ) throws MqttPersistenceException { checkIsOpen ( ) ; File file = new File ( clientDir , key + MESSAGE_FILE_EXTENSION ) ; if ( file . exists ( ) ) { file . delete ( ) ; } }
deletes the data with the specified key from the previously specified persistence directory .
