Q: Type of listener for updates to given cells/columns in JTable and incrementing focus I am trying to use a JTable with the first column predefined.  The user enters data into the 2nd column only (Quantity).  Then I calculate the final income by multiplying the Service and Quantity columns and display it in the third column, Income.

|Service | Quantity | Income
|$40.00  | X        | 
|$40.00  | 3        | 120 


Here user inputs "3" because she did "3" of service X today at $40 each. The user can only update the Quantity column. The Income column will be calculated by the system.
What type of listener should I use?  I was using a TableModelListener but when I want to update Income to 120 by calling setValue = $120 it fires off a TableListenerEvent and hence an infinite loop.
Should I use an ActionEvent, a ColumnListener or something else?
Also, I want the "focus" to increment down the rows, always staying on the second column (the column the user edits).

A: for Listning changes into TableCell you have to implements TableModelListener for example

import java.awt.event.KeyEvent;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.table.*;

public class TableProcessing extends JFrame {

    private static final long serialVersionUID = 1L;
    private JTable table;
    private String[] columnNames = {"Item", "Quantity", "Price", "Cost"};
    private Object[][] data = {
        {"Bread", new Integer(1), new Double(1.11), new Double(1.11)},
        {"Milk", new Integer(1), new Double(2.22), new Double(2.22)},
        {"Tea", new Integer(1), new Double(3.33), new Double(3.33)},
        {"Cofee", new Integer(1), new Double(4.44), new Double(4.44)}};
    private TableModelListener tableModelListener;

    public TableProcessing() {
        DefaultTableModel model = new DefaultTableModel(data, columnNames);
        table = new JTable(model) {

            private static final long serialVersionUID = 1L;

            @Override// Returning the Class of each column will allow different renderers
            public Class getColumnClass(int column) { // to be used based on Class
                return getValueAt(0, column).getClass();
            }

            @Override //  The Cost is not editable
            public boolean isCellEditable(int row, int column) {
                int modelColumn = convertColumnIndexToModel(column);
                return (modelColumn == 3) ? false : true;
            }
        };
        table.setPreferredScrollableViewportSize(table.getPreferredSize());
        //http://stackoverflow.com/questions/7188179/jtable-focus-query/7193023#7193023
        table.setCellSelectionEnabled(true);
        KeyStroke tab = KeyStroke.getKeyStroke(KeyEvent.VK_TAB, 0);
        InputMap map = table.getInputMap(JTable.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT);
        map.put(tab, "selectNextRowCell");
        //http://stackoverflow.com/questions/7188179/jtable-focus-query/7193023#7193023
        JScrollPane scrollPane = new JScrollPane(table);
        getContentPane().add(scrollPane);
        setTableModelListener();
    }

    private void setTableModelListener() {
        tableModelListener = new TableModelListener() {

            @Override
            public void tableChanged(TableModelEvent e) {
                if (e.getType() == TableModelEvent.UPDATE) {
                    System.out.println("Cell " + e.getFirstRow() + ", "
                            + e.getColumn() + " changed. The new value: "
                            + table.getModel().getValueAt(e.getFirstRow(),
                            e.getColumn()));
                    int row = e.getFirstRow();
                    int column = e.getColumn();
                    if (column == 1 || column == 2) {
                        TableModel model = table.getModel();
                        int quantity = ((Integer) model.getValueAt(row, 1)).intValue();
                        double price = ((Double) model.getValueAt(row, 2)).doubleValue();
                        Double value = new Double(quantity * price);
                        model.setValueAt(value, row, 3);
                    }
                }
            }
        };
        table.getModel().addTableModelListener(tableModelListener);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                TableProcessing frame = new TableProcessing();
                frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }
}

