code: protected boolean validate(Validator validator, UIObject ui) {
  
          if (notifiedWidgets.containsKey(validator))
              ui = notifiedWidgets.get(validator);
  
          String msg = validator.validate();
          if (msg == null || msg.length() == 0) {
              validationStyles(validator, null, ui, true);
              return true;
          } else {
              validationStyles(validator, msg, ui, false);
              return false;
          }
      }
docs: Perform validation for a single validator
  
  @param ui the {@link UIObject} to change the stylesheet on
  @return true if this validator was successfully applied or false otherwise