JTable and the ****** TableModel

Question

Ok, I know I'm messing with all of these threads about table and table model but there is no way for me to understand:
I do
MyTable table = new MyTable( rowData, column );
public class MyTable extends JTabel {
MyTableModel myMod = null;
public MyTable( Vector vec1, Vector vec2 ) {
super();
myMod = new MyModel( vec1, vec2 );
setModel( myMod);
public class MyModel extends DefaultTableModel {
public MyModel( Vector vec1, Vector vec2 ) { super(vec1,vec2); }
but my tables are empty (1)
and I can't add rows (2)
Why? I'm messing with this for a lot.. could some one very kind post a bit of code that make me understand what is right and what is not right?
thanks in advance

Answer 1

Try this out, and you will probably figure out what you're doing wrong.
* TableRenderDemo.java is a 1.4 application that requires no other files.
import javax.swing.DefaultCellEditor;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.AbstractTableModel;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.TableCellRenderer;
import javax.swing.table.TableColumn;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.GridLayout;
* TableRenderDemo is just like TableDemo, except that it
* explicitly initializes column sizes and it uses a combo box
* as an editor for the Sport column.
public class TableRenderDemo extends JPanel {
    private boolean DEBUG = false;
    public TableRenderDemo() {
        super(new GridLayout(1,0));
        JTable table = new JTable(new MyTableModel());
        table.setPreferredScrollableViewportSize(new Dimension(500, 70));
        //Create the scroll pane and add the table to it.
        JScrollPane scrollPane = new JScrollPane(table);
        //Set up column sizes.
        initColumnSizes(table);
        //Fiddle with the Sport column's cell editors/renderers.
        setUpSportColumn(table, table.getColumnModel().getColumn(2));
        //Add the scroll pane to this panel.
        add(scrollPane);
     * This method picks good column sizes.
     * If all column heads are wider than the column's cells'
     * contents, then you can just use column.sizeWidthToFit().
    private void initColumnSizes(JTable table) {
        MyTableModel model = (MyTableModel)table.getModel();
        TableColumn column = null;
        Component comp = null;
        int headerWidth = 0;
        int cellWidth = 0;
        Object[] longValues = model.longValues;
        TableCellRenderer headerRenderer =
            table.getTableHeader().getDefaultRenderer();
        for (int i = 0; i < 5; i++) {
            column = table.getColumnModel().getColumn(i);
            comp = headerRenderer.getTableCellRendererComponent(
                                 null, column.getHeaderValue(),
                                 false, false, 0, 0);
            headerWidth = comp.getPreferredSize().width;
            comp = table.getDefaultRenderer(model.getColumnClass(i)).
                             getTableCellRendererComponent(
                                 table, longValues,
false, false, 0, i);
cellWidth = comp.getPreferredSize().width;
if (DEBUG) {
System.out.println("Initializing width of column "
+ i + ". "
+ "headerWidth = " + headerWidth
+ "; cellWidth = " + cellWidth);
//XXX: Before Swing 1.1 Beta 2, use setMinWidth instead.
column.setPreferredWidth(Math.max(headerWidth, cellWidth));
public void setUpSportColumn(JTable table,
TableColumn sportColumn) {
//Set up the editor for the sport cells.
JComboBox comboBox = new JComboBox();
comboBox.addItem("Snowboarding");
comboBox.addItem("Rowing");
comboBox.addItem("Knitting");
comboBox.addItem("Speed reading");
comboBox.addItem("Pool");
comboBox.addItem("None of the above");
sportColumn.setCellEditor(new DefaultCellEditor(comboBox));
//Set up tool tips for the sport cells.
DefaultTableCellRenderer renderer =
new DefaultTableCellRenderer();
renderer.setToolTipText("Click for combo box");
sportColumn.setCellRenderer(renderer);
class MyTableModel extends AbstractTableModel {
private String[] columnNames = {"First Name",
"Last Name",
"Sport",
"# of Years",
"Vegetarian"};
private Object[][] data = {
{"Mary", "Campione",
"Snowboarding", new Integer(5), new Boolean(false)},
{"Alison", "Huml",
"Rowing", new Integer(3), new Boolean(true)},
{"Kathy", "Walrath",
"Knitting", new Integer(2), new Boolean(false)},
{"Sharon", "Zakhour",
"Speed reading", new Integer(20), new Boolean(true)},
{"Philip", "Milne",
"Pool", new Integer(10), new Boolean(false)}
public final Object[] longValues = {"Sharon", "Campione",
"None of the above",
new Integer(20), Boolean.TRUE};
public int getColumnCount() {
return columnNames.length;
public int getRowCount() {
return data.length;
public String getColumnName(int col) {
return columnNames[col];
public Object getValueAt(int row, int col) {
return data[row][col];
* JTable uses this method to determine the default renderer/
* editor for each cell. If we didn't implement this method,
* then the last column would contain text ("true"/"false"),
* rather than a check box.
public Class getColumnClass(int c) {
return getValueAt(0, c).getClass();
* Don't need to implement this method unless your table's
* editable.
public boolean isCellEditable(int row, int col) {
//Note that the data/cell address is constant,
//no matter where the cell appears onscreen.
if (col < 2) {
return false;
} else {
return true;
* Don't need to implement this method unless your table's
* data can change.
public void setValueAt(Object value, int row, int col) {
if (DEBUG) {
System.out.println("Setting value at " + row + "," + col
+ " to " + value
+ " (an instance of "
+ value.getClass() + ")");
data[row][col] = value;
fireTableCellUpdated(row, col);
if (DEBUG) {
System.out.println("New value of data:");
printDebugData();
private void printDebugData() {
int numRows = getRowCount();
int numCols = getColumnCount();
for (int i=0; i < numRows; i++) {
System.out.print(" row " + i + ":");
for (int j=0; j < numCols; j++) {
System.out.print(" " + data[i][j]);
System.out.println();
System.out.println("--------------------------");
* Create the GUI and show it. For thread safety,
* this method should be invoked from the
* event-dispatching thread.
private static void createAndShowGUI() {
//Make sure we have nice window decorations.
JFrame.setDefaultLookAndFeelDecorated(true);
//Create and set up the window.
JFrame frame = new JFrame("TableRenderDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Create and set up the content pane.
TableRenderDemo newContentPane = new TableRenderDemo();
newContentPane.setOpaque(true); //content panes must be opaque
frame.setContentPane(newContentPane);
//Display the window.
frame.pack();
frame.setVisible(true);
public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
Good luck!!