sorting a JTable using getColumnClass() when connected to JDBC

Question

I have spent a few days trying to get my JTable sorting correctly. I know the code I have to use, but cannot seem to get it for 'fit' and work into my code. I am getting the TableModel data from a database so if i call the getColumnClass() when initalising the model, I get a NullPointerException (of course), but I can't seem to get the getColumnClass(int) to work anywhere else such as model.getColumnClass(columnIndex). I only need to sort the first column in numerical order as the rest are strings. Here is my code. (ps: this is the first time using JBDC so I most likely have errors in the order I am calling - or maybe doing it in 'longhand' haha)

    public JTable memberList() 
        {
            JTable jTable1;
            DefaultTableModel model;
            model = new DefaultTableModel(); 
            jTable1 = new JTable(model);
            TableRowSorter sorter = new TableRowSorter(model);

            try 
            {
                Statement stmt = conn.createStatement();
                String sql = "select    rm.race_no,cm.firstname,cm.lastname,cm.phone,cm.dob,cm.email,cm.TwinTown_ID,rm.disqualified,cm.notes\n" +
                             "from competitor_master cm join competitor_season cs on cm.competitor_id = cs.competitor_id\n" +
                             "inner join race_master rm on cs.race_no= rm.race_no where cm.twintown_id is not null and cs.season_start_year in (year(sysdate()))\n" +
                             "group by (race_no);";
                ResultSet rs = stmt.executeQuery(sql);

                String b = "", c = "", d = "", e = "", f = "", g = "", h = "", i = "";
                int a;

                model.addColumn("Member Number");
                model.addColumn("First Name");
                model.addColumn("Last Name");
                model.addColumn("Phone");
                model.addColumn("Date of Birth");
                model.addColumn("Email");
                model.addColumn("TT Member Number");
                model.addColumn("Disqualified");
                model.addColumn("Notes");


                while(rs.next())
                {
                    a = rs.getInt(1);
                    b = rs.getString("FirstName");
                    c = rs.getString("LastName");
                    d = rs.getString("phone");
                    e = rs.getString("dob");
                    f = rs.getString("email");
                    g = rs.getString("TwinTown_ID");
                    h = rs.getString("disqualified");
                    i = rs.getString("notes");
                    model.addRow(new Object[] {a,b,c,d,e,f,g,h,i});
                    model.getColumnClass(1);

                }

                stmt.close();
                rs.close();

            }
            catch (SQLException ex)
            {

            }

                jTable1.getTableHeader().setFont(new Font("Microsoft Tai Le", Font.BOLD, 14));
                jTable1.getTableHeader().setBackground(Color.WHITE);
                jTable1.getTableHeader().setForeground(new Color(234, 168, 82));
                jTable1.getTableHeader().setBorder(null);


            jTable1.setRowSorter(sorter);
            return jTable1;

        }

    public Class getColumnClass (int column){
            if (column==1) {
                return(Integer.class);
            }
            return(String.class);
        }

Why do you need to call getColumnClass? Why do you need to recreate the JTable each time you call the method? — MadProgrammer
– MadProgrammer, Commented Sep 27, 2015 at 5:38
Well, as I said, I'm new to this, but I thought I needed to call the getColumnClass so the the rowSorter knew how to sort the row (numerically - int or alphabetically - string). I'm not sure why I need to recreate the JTable each time I call the method - I think I'm trying one step at a time, the next is to try the documentListener to dynamically sort the rows on user input.. I have the GUI in a different class (UserInterface) and I have this code in the dataHandler class. so when it is called it is memberTable = dh.memberList(); Sorry, I don't think I'm making much sense :-( — AngeKing
– AngeKing, Commented Sep 27, 2015 at 6:12
So, i've taken out any reference to the columnClass and it is sorting but by the first number only. so is sorting like this: 123 17 22 28 45 5 56 66 — AngeKing
– AngeKing, Commented Sep 27, 2015 at 6:24

camickr · Accepted Answer · 2015-09-27 17:01:37Z

1

it is sorting but by the first number only. so is sorting like this: 123 17 22 28 45 5 56 66

Because it is treating all data as String data.

model = new DefaultTableModel(); 
jTable1 = new JTable(model);

You are using the default implementation of the DefaultTableModel and the JTable. The default implementation of the getColumnClass(...) method just returns Object.class so the toString() value of each object is sorted.

You don't invoke the getColumnClass() method manually, you need to override the getColumnClass(...) method of your TableModel:

model = new DefaultTableModel()
{
    @Override
    public Class getColumnClass (int column)
    {
        return (column == 0) ? Integer.class : String.class;
    }
};

answered Sep 27, 2015 at 17:01

camickr

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