🚀 go-pugleaf

Hello,

I have a JTable whose TableModel stores data in an ArrayList of ArrayLists. 
Perhaps because I am more used to C++ (where I know exactly where my data 
resides), I am having trouble editing cell entries.

Stripped to its essentials, the code to edit an entry is as follows, where 
ds is an instance of an implemented AbstractTableModel

            Element elem = (Element) ds.getObjectAt(gridrow, gridcol);
            eresults.copy(elem.results); 
//puts new results into elem.results
            ds.setValueAt((Object) elem,gridrow,gridcol);

Again stripping out all of the code to handle error checking and such, 
getObjectAt is equivalent to two lines:

            ArrayList aRow = (ArrayList) table.get(gridrow);
            return ( aRow.get(columnIndex) );

and setValueAt to two lines

            ArrayList aRow = (ArrayList) table.get(gridrow);
            aRow.set(gridcol, elem);


Now for the dumb questions.  When I have ds.getObjectAt(gridrow, gridcol), 
am I getting a new copy of the data, or a reference to the existing data? 
When I have ds.setValueAt((Object) elem,gridrow,gridcol), is Java creating a 
new copy of elem, or is the ArrayList now pointing to the local object?  If 
it is the second case, then it would seem like I don't really need to call 
setValueAt, except for the side-effect of calling fireTableCellUpdated().

Thanks,
Richard