code: protected String describe(final FieldExpression fieldExpression, final boolean and) {
          Preconditions.checkNotNull(fieldExpression, "CronFieldExpression should not be null!");
          if (fieldExpression instanceof Always) {
              return describe(fieldExpression, and);
          }
          if (fieldExpression instanceof And) {
              return describe((And) fieldExpression);
          }
          if (fieldExpression instanceof Between) {
              return describe(fieldExpression, and);
          }
          if (fieldExpression instanceof Every) {
              return describe((Every) fieldExpression, and);
          }
          if (fieldExpression instanceof On) {
              return describe((On) fieldExpression, and);
          }
          return StringUtils.EMPTY;
      }
docs: Given a CronFieldExpression, provide a String with a human readable description.
  Will identify CronFieldExpression subclasses and delegate.
  
  @param fieldExpression - CronFieldExpression instance - not null
  @param and             - boolean expression that indicates if description should fit an "and" context
  @return human readable description - String