output: #fixed code
                                  @Override
      public void addConfigListener(String dataId, ConfigChangeListener listener) {
          configListenersMap.putIfAbsent(dataId, new ArrayList<>());
          configChangeNotifiersMap.putIfAbsent(dataId, new ArrayList<>());
          ConfigChangeNotifier configChangeNotifier = new ConfigChangeNotifier(dataId, listener);
          configChangeNotifiersMap.get(dataId).add(configChangeNotifier);
          if (null != listener.getExecutor()) {
              listener.getExecutor().submit(configChangeNotifier);
          } else {
              consulNotifierExecutor.submit(configChangeNotifier);
          }
      }
input: #vulnerable code 
                                  @Override
      public void addConfigListener(String dataId, ConfigChangeListener listener) {
          configListenersMap.putIfAbsent(dataId, new ArrayList<>());
          configChangeNotifiersMap.putIfAbsent(dataId, new ArrayList<>());
          ConfigChangeNotifier configChangeNotifier = new ConfigChangeNotifier(dataId, listener);
          configChangeNotifiersMap.get(dataId).add(configChangeNotifier);
          if (null != listener.getExecutor()) {
              listener.getExecutor().submit(configChangeNotifier);
          } else {
              consulConfigExecutor.submit(configChangeNotifier);
          }
      } 
                              #location 3 
                              #vulnerability type THREAD_SAFETY_VIOLATION