question: protected AbstractCategoryItemLabelGenerator ( String labelFormat , DateFormat formatter ) { ParamChecks . nullNotPermitted ( labelFormat , "labelFormat" ) ; ParamChecks . nullNotPermitted ( formatter , "formatter" ) ; this . labelFormat = labelFormat ; this . numberFormat = null ; this . percentFormat = NumberFormat . getPercentInstance ( ) ; this . dateFormat = formatter ; this . nullValueString = "-" ; }
target:  Creates a label generator with the specified date formatter.