code: private synchronized Set<FilterModel> findFilterModels(
  			final Class<? extends Filter> filterClass) {
  		Set<FilterModel> foundFilterModels = null;
  		for (FilterModel filterModel : filterModels.values()) {
  			if (filterModel.getFilterClass() != null
  					&& filterModel.getFilterClass().equals(filterClass)) {
  				if (foundFilterModels == null) {
  					foundFilterModels = new HashSet<>();
  				}
  				foundFilterModels.add(filterModel);
  			}
  		}
  		return foundFilterModels;
  	}
docs: /*
  private synchronized Set<Filter> findFilter(
  final Class<? extends Filter> filterClass) {
  Set<Filter> foundFilterModels = null;
  for (FilterModel filterModel : filterModels) {
  if (filterModel.getFilterClass() != null
  && filterModel.getFilterClass().equals(filterClass)) {
  if (foundFilterModels == null) {
  foundFilterModels = new HashSet<Filter>();
  }
  foundFilterModels.add(filterModel.getFilter());
  }
  }
  return foundFilterModels;
  }