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Why I can't catch NumberFormatException in the tableModel

Renee Zhang
Ranch Hand

Joined: Sep 10, 2001
Posts: 72
Here is some source code from swing tutorial. ( I find it can't catch the NumberFormatException at column[3]. When I enter a String into column[3], the cell's border turns red and the table is dead. Can anyone tell me why? Any consideration will be greatly appreciated!
import javax.swing.JTable;
import javax.swing.table.AbstractTableModel;
import javax.swing.table.TableColumn;
import javax.swing.DefaultCellEditor;
import javax.swing.table.TableCellRenderer;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.JScrollPane;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;
import javax.swing.JOptionPane;
import java.awt.*;
import java.awt.event.*;
public class TableRenderDemo extends JFrame {
private boolean DEBUG = true;
public TableRenderDemo() {
MyTableModel myModel = new MyTableModel();
JTable table = new JTable(myModel);
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, myModel);
//Fiddle with the Sport column's cell editors/renderers.
//Add the scroll pane to this window.
getContentPane().add(scrollPane, BorderLayout.CENTER);
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
* 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) {
TableColumn column = null;
Component comp = null;
int headerWidth = 0;
int cellWidth = 0;
Object[] longValues = model.longValues;
for (int i = 0; i < 5; i++) {
column = table.getColumnModel().getColumn(i);
try {
comp = column.getHeaderRenderer().
null, column.getHeaderValue(),
false, false, 0, 0);
headerWidth = comp.getPreferredSize().width;
} catch (NullPointerException e) {
System.err.println("Null pointer exception!");
System.err.println(" getHeaderRenderer returns null in 1.3.");
System.err.println(" The replacement is getDefaultRenderer.");
comp = table.getDefaultRenderer(model.getColumnClass(i)).
table, longValues[i],
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(TableColumn sportColumn) {
//Set up the editor for the sport cells.
JComboBox comboBox = new JComboBox();
comboBox.addItem("Chasing toddlers");
comboBox.addItem("Speed reading");
comboBox.addItem("Teaching high school");
sportColumn.setCellEditor(new DefaultCellEditor(comboBox));
//Set up tool tips for the sport cells.
DefaultTableCellRenderer renderer =
new DefaultTableCellRenderer();
renderer.setToolTipText("Click for combo box");
//Set up tool tip for the sport column header.
TableCellRenderer headerRenderer = sportColumn.getHeaderRenderer();
if (headerRenderer instanceof DefaultTableCellRenderer) {
"Click the sport to see a list of choices");
class MyTableModel extends AbstractTableModel {
final String[] columnNames = {"First Name",
"Last Name",
"# of Years",
final Object[][] data = {
{"Mary", "Campione",
"Snowboarding", new Integer(5), new Boolean(false)},
{"Alison", "Huml",
"Rowing", new Integer(3), new Boolean(true)},
{"Kathy", "Walrath",
"Chasing toddlers", new Integer(2), new Boolean(false)},
{"Mark", "Andrews",
"Speed reading", new Integer(20), new Boolean(true)},
{"Angela", "Lih",
"Teaching high school", new Integer(4), new Boolean(false)}
public final Object[] longValues = {"Angela", "Andrews",
"Teaching high school",
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() + ")");
if (data[0][col] instanceof Integer
&& !(value instanceof Integer)) {
//With JFC/Swing 1.1 and JDK 1.2, we need to create
//an Integer from the value; otherwise, the column
//switches to contain Strings. Starting with v 1.3,
//the table automatically converts value to an Integer,
//so you only need the code in the 'else' part of this
//'if' block.
try {
data[row][col] = new Integer(value.toString());
fireTableCellUpdated(row, col);
} catch (NumberFormatException e) {
"The \"" + getColumnName(col)
+ "\" column accepts only integer values.");
} else {
data[row][col] = value;
fireTableCellUpdated(row, col);
if (DEBUG) {
System.out.println("New value of data:");
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]);
public static void main(String[] args) {
TableRenderDemo frame = new TableRenderDemo();
Paul Stevens
Ranch Hand

Joined: May 17, 2001
Posts: 2823
This is just a preference of mine. I would create an editor and not allow invalid data in the first place.

ps When posting code, use the code tags.
It is sorta covered in the JavaRanch Style Guide.
subject: Why I can't catch NumberFormatException in the tableModel