question: @ SuppressWarnings ( "unchecked" ) public EnumeratedData ( DataSource original , double offset , double steps ) { this . original = original ; this . offset = offset ; this . steps = steps ; Class < ? extends Comparable < ? > > [ ] typesOrig = original . getColumnTypes ( ) ; Class < ? extends Comparable < ? > > [ ] types = new Class [ typesOrig . length + 1 ] ; System . arraycopy ( typesOrig , 0 , types , 1 , typesOrig . length ) ; types [ 0 ] = Double . class ; setColumnTypes ( types ) ; original . addDataListener ( this ) ; }
target:  Initializes a new data source based on an original data source which will contain an additional column which enumerates all rows. The enumeration will start at a specified offset and will have a specified step size.