Index - J
| join | DataFrame.Operations.Join, DataFrame | 
| jointBincount | DataFrame.Internal.Statistics | 
| JoinType | DataFrame.Operations.Join, DataFrame | 
| JSON_TYPE | DataFrame.IO.Parquet.Types | 
| julianDayAndNanosToUTCTime | DataFrame.IO.Parquet.Time | 
| julianDayToDay | DataFrame.IO.Parquet.Time |