在Jtable列上添加值

Question

I want to add how many items in the unit count and compute it in the total cost.

private void display()
{
    DefaultTableModel model= (DefaultTableModel)SupplyRSTable.getModel();
        SupplyRSTable.revalidate();
        model.getDataVector().removeAllElements();
        try{

         stmt = conn.createStatement();
     stmt.executeQuery("SELECT itemcode,itemname,itemgroup,itemcost FROM supplytable");
     rs = stmt.getResultSet();
        while (rs.next()) 
        {
                    String r1 = rs.getString("itemname");
                    String r2 = rs.getString("itemgroup");
                    String r3 = rs.getString("itemcost");
                    String r4 = rs.getString("itemcode");
                   model.addRow(new Object[] {r4,r1,r2,r3}); 
                   SupplyRSTable.revalidate(); 

        }
        }
        catch(Exception e)
        {
            JOptionPane.showMessageDialog(null, e.getMessage());
        }`

I only have a display

Answer 1

1: you formated your code wrong; only part of it is formatted in this post.

2: I'm assuming your database that your are pulling from has a column which has the unit count so the query should be something like :

stmt.executeQuery("SELECT itemcode,itemname,itemgroup,itemcost,itemcount FROM supplytable");

The idea is to create that total column using previous value of item cost and item count that is already there so it should look like this:

String r1 = rs.getString("itemname");
String r2 = rs.getString("itemgroup");
String r3 = rs.getString("itemcost");
String r4 = rs.getString("itemcode");
String r5 = rs.getString("itemcount");
Integer cost= Integer.parseInt(r5);
Integer amount=Integer.parseInt(r3);
Integer total=cost*amount;
String r6=Integer.toString(total);
model.addRow(new Object[] {r4,r1,r2,r3,r5,r6});
SupplyRSTable.revalidate(); 

of course Multiplying an Integer Cost by an Amount could give rise to decimal value such as 31.43$ so you can/should replace the total variable with a Double and you would need to change r6 Integer parsing aswell in this case.