code: private boolean hasConstantField (ClassDoc classDoc) {
          VisibleMemberMap visibleMemberMapFields = new VisibleMemberMap(classDoc,
              VisibleMemberMap.FIELDS, configuration);
          List<?> fields = visibleMemberMapFields.getLeafClassMembers(configuration);
          for (Object f : fields) {
              FieldDoc field = (FieldDoc) f;
              if (field.constantValueExpression() != null) {
                  classDocsWithConstFields.add(classDoc);
                  return true;
              }
          }
          return false;
      }
docs: Return true if the given class has constant fields to document.
  
  @param classDoc the class being checked.
  @return true if the given package has constant fields to document.