code: public Pair<Boolean,Object> hasValueChanged(String fieldId) {
          for (int i = 0; i < changedFields.length; i++) {
              String changedField = changedFields[i];
              if ( fieldId.equals(changedField) ) {
                  return new Pair<>(true,oldValues[i]);
              }
          }
          return new Pair<>(false,null);
      }
docs: return wether field is in changedfieldlist and old value of this field
  @param fieldId
  @return