JTable SelectionModel - first Index and Las Index giving incorrect values

Question

Hi Guys,
When i added a ListSelectionListener to the JTable's selectionModel, and tried to get the first index and last index values. The goofy thing i noticed is when you select different rows, the indexes are correct,but when you switch between the same rows, then indexes provided by the ListSelectionListener are always the same. Example : if you switch between 3 and 4 rows first index is 2 and last index is 3 which is correct, but if you go back 3rd row from 4th row, the first index is still 2 and last index is 3... which is kind of weird.
Any ideas about this, and why this is happenning.
I am pasting my sample code here any explanation is very helpfull to understand this behavior
Thanks
Nicedude
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JComponent;
import javax.swing.ListSelectionModel;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
* SimpleTableSelectionDemo is just like SimpleTableDemo,
* except that it detects selections, printing information
* about the current selection to standard output.
public class SimpleTableSelectionDemo extends JPanel {
     private boolean DEBUG = false;
     private boolean ALLOW_COLUMN_SELECTION = false;
     private boolean ALLOW_ROW_SELECTION = true;
     public SimpleTableSelectionDemo() {
          super(new GridLayout(1,0));
          final String[] columnNames = {"First Name",
                    "Last Name",
                    "Sport",
                    "# of Years",
          "Vegetarian"};
          final 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)}
          final JTable table = new JTable(data, columnNames);
          table.setPreferredScrollableViewportSize(new Dimension(500, 70));
          table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
          if (ALLOW_ROW_SELECTION) { // true by default
               ListSelectionModel rowSM = table.getSelectionModel();
               rowSM.addListSelectionListener(new ListSelectionListener() {
                    public void valueChanged(ListSelectionEvent e) {
                         //Ignore extra messages.
                         if (e.getValueIsAdjusting()) return;
                         ListSelectionModel lsm = (ListSelectionModel)e.getSource();
                         if (lsm.isSelectionEmpty()) {
                              System.out.println("No rows are selected.");
                         } else {
                              int selectedRow = lsm.getMinSelectionIndex();
                         System.out.println("Row " + selectedRow + " is now selected.");
                              int first = e.getFirstIndex();
                                                        int last = e.getLastIndex();
                          System.out.println(" First Index is : " + first);
                          System.out.println(" Last Index is : " + last );
          } else {
               table.setRowSelectionAllowed(false);
          if (ALLOW_COLUMN_SELECTION) { // false by default
               if (ALLOW_ROW_SELECTION) {
                    //We allow both row and column selection, which
                    //implies that we *really* want to allow individual
                    //cell selection.
                    table.setCellSelectionEnabled(true);
               table.setColumnSelectionAllowed(true);
               ListSelectionModel colSM =
                    table.getColumnModel().getSelectionModel();
               colSM.addListSelectionListener(new ListSelectionListener() {
                    public void valueChanged(ListSelectionEvent e) {
                         //Ignore extra messages.
                         if (e.getValueIsAdjusting()) return;
                         ListSelectionModel lsm = (ListSelectionModel)e.getSource();
                         if (lsm.isSelectionEmpty()) {
                              System.out.println("No columns are selected.");
                         } else {
                              int selectedCol = lsm.getMinSelectionIndex();
                              System.out.println("Column " + selectedCol
                                        + " is now selected.");
          if (DEBUG) {
               table.addMouseListener(new MouseAdapter() {
                    public void mouseClicked(MouseEvent e) {
                         printDebugData(table);
          //Create the scroll pane and add the table to it.
          JScrollPane scrollPane = new JScrollPane(table);
          //Add the scroll pane to this panel.
          add(scrollPane);
     private void printDebugData(JTable table) {
          int numRows = table.getRowCount();
          int numCols = table.getColumnCount();
          javax.swing.table.TableModel model = table.getModel();
          System.out.println("Value of data: ");
          for (int i=0; i < numRows; i++) {
               System.out.print("    row " + i + ":");
               for (int j=0; j < numCols; j++) {
                    System.out.print("  " + model.getValueAt(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("SimpleTableSelectionDemo");
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          //Create and set up the content pane.
          SimpleTableSelectionDemo newContentPane = new SimpleTableSelectionDemo();
          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();
}

Answer 1

>
I was (maybe wrongly) under the impression that, last index will give the last selected value and first index will give me the currect selected value. Not maybe - your impression sure is wrong. Honestly can't understand how it's possible to mis-interpret the api doc of ListSelectionEvent (except not reading it ;-)
"Represents a change in selection status between firstIndex and
lastIndex, inclusive. firstIndex is less than or equal to
lastIndex. The selection of at least one index within the range will
have changed."
Jeanette