code: public boolean checkItemStatus(String listId, int mediaId) throws MovieDbException {
          TmdbParameters parameters = new TmdbParameters();
          parameters.add(Param.ID, listId);
          parameters.add(Param.MOVIE_ID, mediaId);
  
          URL url = new ApiUrl(apiKey, MethodBase.LIST).subMethod(MethodSub.ITEM_STATUS).buildUrl(parameters);
          String webpage = httpTools.getRequest(url);
  
          try {
              return MAPPER.readValue(webpage, ListItemStatus.class).isItemPresent();
          } catch (IOException ex) {
              throw new MovieDbException(ApiExceptionType.MAPPING_FAILED, "Failed to get item status", url, ex);
          }
      }
docs: Check to see if an ID is already on a list.
  
  @param listId
  @param mediaId
  @return true if the movie is on the list
  @throws MovieDbException