I don't use jlink but here is an excerpt from the user manual -

Dimension Objects

Dimension objects include standard PTC Creo Parametric dimensions as well as reference dimensions. Dimension objects enable you to access dimension tolerances and enable you to set the value for the dimension. Reference dimensions allow neither of these actions.

Getting Dimensions

Dimensions and reference dimensions are PTC Creo Parametric model items. See the section Getting ModelItem Objects on page 208 for methods that can return Dimension and RefDimension objects.

Dimension Information

Methods Introduced:

• pfcModelItem.BaseParameter.GetValue

• pfcModelItem.BaseParameter.SetValue

• pfcModelItem.BaseDimension.GetDimValue

• pfcModelItem.BaseDimension.SetDimValue

• pfcModelItem.BaseParameter.GetIsDesignated

• pfcModelItem.BaseParameter.SetIsDesignated

• pfcModelItem.BaseParameter.GetIsModified

• pfcModelItem.BaseParameter.ResetFromBackup

• pfcModelItem.BaseParameter.GetIsRelationDriven

• pfcDimension.BaseDimension.GetDimType

• pfcDimension.BaseDimension.GetSymbol

• pfcDimension.BaseDimension.GetTexts

• pfcDimension.BaseDimension.SetTexts

All the BaseParameter methods are accessible to Dimensions as well as Parameters. See the section Parameter Objects on page 257 for brief descriptions.

Note

You cannot set the value or designation status of reference dimension objects.

Apologies for copy/paste formatting