Develop Reference

JTable prevent Strings

How can I prevent strings in a JTable and allow and show only numbers?
like for example I press "a" on my keyboard I won't not even that "a" will be displayed in the JTable cell. literally nothing should happen unless a user types in a number. so how can I prevent even not showing "a" ?

I had a similar issue some time ago and solved by validating with an KeyListener. This is a dirty way of doing it, but it works. The only weakness is if you're trying to edit a lot of cells quickly if you're a fast writer. Anyhow, here's the code that worked for me. I've added some commentary, but in short; we're overriding the normal validation and check with a TextField KeyListener if the given key is the one we allow in the TextField. If we allow the key, we enable TextField editing, if not, we turn it off to prevent the character being printed in the TextField. I hope this helps you.
UPDATE 1:
adding a celleditor on the TestField to prevent premature data insertion.
public class TableValidation extends JFrame
{
public static void main(String args[])
{
TableValidation x = new TableValidation();
x.setVisible(true);
}
JPanel topPanel;
JTable table = new JTable();
JScrollPane scrollPane;
String[] columnNames;
String[][] dataValues;
public TableValidation()
{
this.setTitle("JTable Cell Validation");
this.setDefaultCloseOperation (EXIT_ON_CLOSE);
this.setSize(300,112);
// make our panel to tin the table to
topPanel = new JPanel();
topPanel.setLayout(new BorderLayout());
this.getContentPane().add(topPanel);
// set some initial data for the table
columnNames = new String[] {"Anything" ,"Numbers only"};
dataValues = new String[][] { {"h4x0r","1337"} };
table.setRowHeight(50);
table.setModel( new CustomTableModel(dataValues, columnNames) );
TableColumn tableColumn = table.getColumnModel().getColumn(1); // apply our validation to the 2nd column
JTextField textfield = new JTextField(); // the textbox to which we test our validation
// setup our validation system. were passing the textfield as out celleditor source
tableColumn.setCellEditor(new MyCellEditor(textfield));
table.setCellSelectionEnabled(true);
scrollPane = new JScrollPane(table);
topPanel.add(scrollPane,BorderLayout.CENTER);
textfield.addKeyListener(new KeyAdapter()
{
public void keyTyped(KeyEvent e)
{
// check what keys can pass our test
if (textfield.isFocusOwner())
if (e.getKeyChar() != KeyEvent.VK_BACK_SPACE) // we allow backspace, obviously
if (!Character.isDigit(e.getKeyChar())) // if key is not a digit.. cancel editing
{
// when it detects an invalid input, set editable to false. this prevents the input to register
textfield.setEditable(false);
textfield.setBackground(Color.WHITE);
return;
}
textfield.setEditable(true);
}
});
}
}
class MyCellEditor extends AbstractCellEditor implements TableCellEditor
{
private static final long serialVersionUID = 1L;
private JTextField textField;
public MyCellEditor(JTextField textField)
{
this.textField=textField;
}
#Override
public boolean isCellEditable(EventObject e)
{
if (super.isCellEditable(e)) {
if (e instanceof MouseEvent) {
MouseEvent me = (MouseEvent) e;
return me.getClickCount() >= 2;
}
if (e instanceof KeyEvent) {
KeyEvent ke = (KeyEvent) e;
return ke.getKeyCode() == KeyEvent.VK_F2;
}
}
return false;
}
#Override
public Object getCellEditorValue()
{
return this.textField.getText();
}
#Override
public Component getTableCellEditorComponent(JTable table, Object value, boolean isSelected, int row, int column)
{
this.textField.setFont(table.getFont());
this.textField.setText(value.toString());
return this.textField;
}
}
class CustomTableModel extends DefaultTableModel
{
CustomTableModel(String[][] data,String[] names)
{
super(data, names);
}
// we always pass true in our tablemodel so we can validate somewhere else
public boolean isCellEditable(int row,int cols)
{
return true;
}
}

Change the font color in a specific cell of a JTable?

Before starting, I've viewed a handful of solutions as well as documentation. I can't seem to figure out why my code isn't working the way I believe it should work. I've extended DefaultTableCellRenderer but I don't believe it is being applied - that or I messed things up somewhere.
Here are the threads / websites I've looked into before posting this question:
Swing - Is it possible to set the font color of 'specific' text within a JTable cell?
JTable Cell Renderer
http://docs.oracle.com/javase/tutorial/uiswing/components/table.html
I realize the first link uses HTML to change the font color, but I would think the way I went about it should produce the same result.
To make it easier on those who want to help me figure out the issues, I've created an SSCCE.
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Font;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.DefaultTableModel;
public class TableTest {
private static final int IMPORTANT_COLUMN = 2;
public static void createAndShowGUI() {
Object[][] data = new Object[2][4];
//create sample data
String[] realRowData = { "1", "One", "1.0.2", "compile" };
String[] fakeRowData = { "2", "Two", "1.3.2-FAKE", "compile" };
//populate sample data
for(int i = 0; i < realRowData.length; i++) {
data[0][i] = realRowData[i];
data[1][i] = fakeRowData[i];
}
//set up tableModel
JTable table = new JTable();
table.setModel(new DefaultTableModel(data,
new String[] { "ID #", "Group #", "version", "Action" })
{
Class[] types = new Class[] {
Integer.class, String.class, String.class, String.class
};
boolean[] editable = new boolean[] {
false, false, true, false
};
#Override
public Class getColumnClass(int columnIndex) {
return types[columnIndex];
}
#Override
public boolean isCellEditable(int rowIndex, int columnIndex) {
return editable[columnIndex];
}
});
//set custom renderer on table
table.setDefaultRenderer(String.class, new CustomTableRenderer());
//create frame to place table
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setMinimumSize(new Dimension(400, 400));
JScrollPane scrollPane = new JScrollPane();
scrollPane.setViewportView(table);
f.add(scrollPane);
f.pack();
f.setVisible(true);
}
//MAIN
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
//Custom DefaultTableCellRenderer
public static class CustomTableRenderer extends DefaultTableCellRenderer {
public Component getTableCellRenderer(JTable table, Object value,
boolean isSelected, boolean hasFocus, int row, int column)
{
Component c = super.getTableCellRendererComponent(table, value, isSelected,
hasFocus, row, column);
String versionVal = table.getValueAt(row, IMPORTANT_COLUMN).toString();
if(versionVal.contains("FAKE")) {
//set to red bold font
c.setForeground(Color.RED);
c.setFont(new Font("Dialog", Font.BOLD, 12));
} else {
//stay at default
c.setForeground(Color.BLACK);
c.setFont(new Font("Dialog", Font.PLAIN, 12));
}
return c;
}
}
}
My goal is to highlight any value in the version column that contains the word FAKE in a red bold text.

I've extended DefaultTableCellRenderer but I don't believe it is being applied
Some simple debugging tips:
Add a simple System.out.println(...) to the method you think should be invoked
When overriding a method, make sure you use the #Override annotation (you used it in the TableModel class, but not your renderer class).
Your problem is a typing mistake because you are not overriding the proper method:
#Override
// public Component getTableCellRenderer(...) // this is wrong
public Component getTableCellRendererComponent(...)
The override annotation will display a compile message. Try it before changing the code.
Also, your first column is NOT an Integer class. Just because it contains String representations of an Integer does not make it an Integer. You need to add an Integer object to the model.

Replace your custom table cell rendere with the below.
Explanations are in comments. Basically, you should override getTableCellRendererComponent then check for correct column (there may be other methods instead of checking header value), then set cell depending on color.
Do not forget last else block to set color to default if it is not the column you want.
//Custom DefaultTableCellRenderer
public static class CustomTableRenderer extends DefaultTableCellRenderer {
// You should override getTableCellRendererComponent
#Override
public Component getTableCellRendererComponent(JTable table, Object value,
boolean isSelected, boolean hasFocus, int row, int column) {
Component c = super.getTableCellRendererComponent(table, value, isSelected,
hasFocus, row, column);
// Check the column name, if it is "version"
if (table.getColumnName(column).compareToIgnoreCase("version") == 0) {
// You know version column includes string
String versionVal = (String) value;
if (versionVal.contains("FAKE")) {
//set to red bold font
c.setForeground(Color.RED);
c.setFont(new Font("Dialog", Font.BOLD, 12));
} else {
//stay at default
c.setForeground(Color.BLACK);
c.setFont(new Font("Dialog", Font.PLAIN, 12));
}
} else {
// Here you should also stay at default
//stay at default
c.setForeground(Color.BLACK);
c.setFont(new Font("Dialog", Font.PLAIN, 12));
}
return c;
}
}

JTable Calls Custom Cell Renderer Method... Continuously

Compilable source can be found at: http://www.splashcd.com/jtable.tar
I'm new to the language, so I'm not sure if this is acceptable behavior or not.
I created a JTable to display a row for each message received (it receives about
one every 20 seconds). One of the table columns can contain a large amount of
text, so I created a custom cell renderer which word wraps and sets the row
height accordingly.
All that works as expected, except that once the table displays its first row,
it calls the cell renderer about ten times a second... until the user closes the
table.
Once I get approx 20 rows in there, the table gets fairly sluggish, taking 2-8
seconds to resize a column, scoll up or down, or render a selected row with the
selected background color.
I inserted a print statement inside the renderer, so I can see how many times
the getTableCellRendererComponent method is being called.
I disabled tool tips, and disabled all cell editing. I do have a listener that
scrolls the view to the last row when either a new row is added or the table is
resized.
Should the getTableCellRendererComponent method be called several times a second
when I'm just viewing the screen (not touching mouse or keyboard)?
TIA

aaaaach
you need doLayout(),
next level :-), then there you can to set Maximum visible rows for JTextComponents too, with little effort
doLayout()
import java.awt.*;
import javax.swing.*;
import javax.swing.table.*;
import javax.swing.text.*;
//http://tips4java.wordpress.com/2008/10/26/text-utilities/
public class AutoWrapTest {
public JComponent makeUI() {
String[] columnNames = {" Text Area Cell Renderer "};
Object[][] data = {
{"123456789012345678901234567890"},
{"dddddddddddddddddddddddddddddddddddddddddddddddddddddddddx"},
{"----------------------------------------------0"},
{">>>>>>>>>>>>>dddddddddddddddddddddddddddddddddddddddddddddddddd"
+ "dddddddxdddddddddddddddddddddddddddddddddddddddddddddd"
+ "dddddddddddx>>>>>>>>>>>>>>>>>>>>>>>>>|"},
{">>>>>>>>>>>>ddddddddddddddddddddddddddddddddddddddddddddddddddd"
+ "ddddddx>>>>>>>>>>>>>>>>>>>>>>>>>>|"},
{"a|"},
{">>>>>>>>bbbb>>>>>>>>>>>>>>>>>>>|"},
{">>>>>>>>>>>>>>>>>>|"},
{">>>>>>>>>>>>>dddddddddddddddddddddddddddddddddddddddddddddddddd"
+ "dddddddxdddddddddddddd123456789012345678901234567890dddddd"
+ "dddddddddddddddddddddddddddddddddddddx>>>>>>>>>>>>>>>>>>>>"
+ ">>>>>|"},
{">>>>>>>>>>>>>dddddddddddddd123456789012345678901234567890dddddd"
+ "dddddddddddddddddddddddddddddddddddddxdddddddddddddd123456"
+ "789012345678901234567890dddddddddddddddddddddddddddddddddd"
+ "ddddd123456789012345678901234567890ddddx>>>>>>>>>>>>>>>>>>"
+ ">>>>>>>|"},};
TableModel model = new DefaultTableModel(data, columnNames) {
private static final long serialVersionUID = 1L;
#Override
public boolean isCellEditable(int row, int column) {
return false;
}
};
JTable table = new JTable(model) {
private static final long serialVersionUID = 1L;
#Override
public void doLayout() {
TableColumn col = getColumnModel().getColumn(0);
for (int row = 0; row < getRowCount(); row++) {
Component c = prepareRenderer(col.getCellRenderer(), row, 0);
if (c instanceof JTextArea) {
JTextArea a = (JTextArea) c;
int h = getPreferredHeight(a) + getIntercellSpacing().height;
if (getRowHeight(row) != h) {
setRowHeight(row, h);
}
}
}
super.doLayout();
}
private int getPreferredHeight(JTextComponent c) {
Insets insets = c.getInsets();
View view = c.getUI().getRootView(c).getView(0);
int preferredHeight = (int) view.getPreferredSpan(View.Y_AXIS);
return preferredHeight + insets.top + insets.bottom;
}
};
table.setEnabled(false);
table.setShowGrid(false);
table.setTableHeader(null);
table.getColumnModel().getColumn(0).setCellRenderer(new TextAreaCellRenderer());
//table.setPreferredScrollableViewportSize(table.getPreferredSize());
JScrollPane sp = new JScrollPane(table);
sp.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
sp.setPreferredSize(new Dimension(250, 533));
JPanel p = new JPanel(new BorderLayout());
p.add(sp);
return p;
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
createAndShowGUI();
}
});
}
public static void createAndShowGUI() {
JFrame f = new JFrame();
f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
f.getContentPane().add(new AutoWrapTest().makeUI());
f.setLocation(100, 100);
f.pack();
f.setVisible(true);
}
}
class TextAreaCellRenderer extends JTextArea implements TableCellRenderer {
private static final long serialVersionUID = 1L;
private final Color evenColor = new Color(230, 240, 255);
public TextAreaCellRenderer() {
super();
setLineWrap(true);
setBorder(BorderFactory.createEmptyBorder(2, 2, 2, 2));
}
#Override
public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
if (isSelected) {
setForeground(table.getSelectionForeground());
setBackground(table.getSelectionBackground());
} else {
setForeground(table.getForeground());
setBackground(table.getBackground());
setBackground((row % 2 == 0) ? evenColor : getBackground());
}
setFont(table.getFont());
setText((value == null) ? "" : value.toString());
return this;
}
}

To get the most performance out of a TableCellRenderer, make sure you're not creating a new instance of a component every time getTableCellRenderer is called. Make the components once and save them as fields of the class.
Also, you'll want to make sure each of the Components you use have the following methods overridden to do nothing:
validate
invalidate
revalidate
repaint
firePropertyChange
(and you probably want to hard code isOpaque).
For more information see: http://docs.oracle.com/javase/6/docs/api/javax/swing/tree/DefaultTreeCellRenderer.html

The problem seems to stem from having JTable's setRowHeight() inside the custom cell renderer, as it calls the custom cell renderer, throwing it into an infinite loop.
I had to add in a check to see if the current row height matched the calculated word wrapped row height. If it did, I didnt try to setRowHeight() again.
Corrected Code:
import java.awt.Component;
import javax.swing.JTable;
import javax.swing.JTextArea;
import javax.swing.UIManager;
import javax.swing.table.TableCellRenderer;
//custom cell renderer for word wrapping, but if you use, you have to
//implement zebra striping functionality which the default renderer has
public class LineWrapCellRenderer extends JTextArea implements TableCellRenderer
{
private int numOfTimesCalled;
#Override
public Component getTableCellRendererComponent(
JTable table,
Object value,
boolean isSelected,
boolean hasFocus,
int row,
int column)
{
System.out.println("Line Wrap Cell Renderer Called: " + numOfTimesCalled++);
System.out.println("row:"+ row + ", col:" + column);
//set up the row size based on the number of newlines in the text in the cell
int fontHeight = this.getFontMetrics(this.getFont()).getHeight();
int numWraps = value.toString().split("\r\n|\r|\n").length;
int rowHeight = fontHeight * numWraps;
//if the calculated rowHeight is the same as the row height of row,
// then don't call setRowHeight again, as doing so will throw us into
// an infinite loop
if(rowHeight != table.getRowHeight(row))
{
table.setRowHeight(row, rowHeight);
//configure word wrapping
setWrapStyleWord(true);
setLineWrap(true);
//use the table's font
setFont(table.getFont());
}
//zebra striping, because whatever cell uses this renderer loses the
//default cell renderer zebra striping
if(isSelected)
{
setBackground(table.getSelectionBackground());
}
else
{
if(row%2 == 1)
{
setBackground(UIManager.getColor("Table.alternateRowColor"));
}
else
{
setBackground(table.getBackground());
}
}
this.setText(value.toString());
return this;
}
}

Nimbus TableHeader was not highlighted as 'pressed'

The JTableHaeder has no 'pressed' highlighting by default. (Nimbus)
NimbusDefaults says it has a default [Pressed] background painter.
What should I do, to see this when i click on the TableHeader?
UPDATE 1
The NimbusStyle.getExtendedState returns the PRESSED on mouseDown correctly. But the NimbusStyle.getBackgroundPainter(SynthContext) returns null cause there is an null in the NimbusStyle.Values cache for the CacheKey "backgroundPainter$$instance" with this state.
What is wrong there?
UPDATE 2
My example shows a JTableHeader and a JScrollBar with an 'Pressed Behavior'.
For the JScrollBar my putClientProperty( "Nimbus.State" ) works with a repaint problem.
public class Header extends JPanel{
public Header() {
super(new BorderLayout());
JTableHeader header = new JTable(5, 3).getTableHeader();
JScrollBar scroll = new JScrollBar(JScrollBar.HORIZONTAL);
add(header, BorderLayout.NORTH);
add(scroll, BorderLayout.SOUTH);
scroll.addMouseListener( new PressedBehavior() );
header.addMouseListener( new PressedBehavior() );
}
static public void main( String[] s ) {
try {
UIManager.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
SwingUtilities.invokeLater( new Runnable() {
#Override
public void run() {
JFrame f = new JFrame("Nimbus Pressed Example");
f.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
f.setBounds( 150, 150, 300, 200 );
f.getContentPane().add( new Header() );
f.setVisible( true );
}
});
} catch( Exception fail ) { /*ignore*/ }
}
private class PressedBehavior extends MouseAdapter {
#Override
public void mouseReleased( MouseEvent e ) {
JComponent source = (JComponent)e.getComponent();
source.putClientProperty( "Nimbus.State", null );
}
#Override
public void mousePressed( MouseEvent e ) {
JComponent source = (JComponent)e.getComponent();
source.putClientProperty( "Nimbus.State", "Pressed" );
//source.invalidate();
//source.repaint();
}
}
}

technically, you need that state on the rendering component, not on the JTableHeader itself:
#Override
public void mousePressed( MouseEvent e ) {
JComponent source = (JComponent)e.getComponent();
source.putClientProperty( "Nimbus.State", "Pressed" );
if (source instanceof JTableHeader) {
((JComponent) ((JTableHeader) source).getDefaultRenderer())
.putClientProperty("Nimbus.State", "Pressed");
}
}
Problem then is that the same instance (of rendering component) is used for all columns, so if you drag a column all appear pressed ...
Edit: couldn't resist to dig a bit ... Nimbus is soooo ... lacking, to put it mildly ;-)
Turns out that the defaults indeed have the styles for pressed, what's missing is the logic to set it. Probably not entirely trivial, because the logic (aka: MouseListener) resides in BasicTableHeaderUI which doesn't know about subclass' painter states. The only thingy the logic is supporting (hot needle fix) is rollover-awareness, but not pressed-ness.
While we can't hook into the logic (well, we could ... but that's another trick :-) we can look for secondary state changes like draggingColumn/resizingColumn (not-bound) properties in JTableHeader and let a custom renderer update itself as appropriate. Here's a line-out of how-to:
public static class WrappingRenderer implements TableCellRenderer {
private DefaultTableCellHeaderRenderer delegate;
private JTableHeader header;
public WrappingRenderer(JTableHeader header) {
this.header = header;
this.delegate = (DefaultTableCellHeaderRenderer) header.getDefaultRenderer();
header.setDefaultRenderer(this);
}
#Override
public Component getTableCellRendererComponent(JTable table,
Object value, boolean isSelected, boolean hasFocus, int row,
int column) {
Component comp = delegate.getTableCellRendererComponent(table,
value, isSelected, hasFocus, row, column);
TableColumn draggedColumn = table.getTableHeader().getDraggedColumn();
if (draggedColumn != null) {
if (table.convertColumnIndexToModel(column) == draggedColumn.getModelIndex()) {
setNimbusState("Pressed");
} else {
setNimbusState(null);
}
} else {
setNimbusState(null);
}
// do similar for resizing column
return comp;
}
public void setNimbusState(String state) {
delegate.putClientProperty("Nimbus.State", state);
}
}

How do I make a list with checkboxes in Java Swing?

What would be the best way to have a list of items with a checkbox each in Java Swing?
I.e. a JList with items that have some text and a checkbox each?

A wonderful answer is this CheckBoxList. It implements Telcontar's answer (though 3 years before :)... I'm using it in Java 1.6 with no problems. I've also added an addCheckbox method like this (surely could be shorter, haven't used Java in a while):
public void addCheckbox(JCheckBox checkBox) {
ListModel currentList = this.getModel();
JCheckBox[] newList = new JCheckBox[currentList.getSize() + 1];
for (int i = 0; i < currentList.getSize(); i++) {
newList[i] = (JCheckBox) currentList.getElementAt(i);
}
newList[newList.length - 1] = checkBox;
setListData(newList);
}
I tried out the demo for the Jidesoft stuff, playing with the CheckBoxList I encountered some problems (behaviors that didn't work). I'll modify this answer if I find problems with the CheckBoxList I linked to.

Create a custom ListCellRenderer and asign it to the JList.
This custom ListCellRenderer must return a JCheckbox in the implementantion of getListCellRendererComponent(...) method.
But this JCheckbox will not be editable, is a simple paint in the screen is up to you to choose when this JCheckbox must be 'ticked' or not,
For example, show it ticked when the row is selected (parameter isSelected), but this way the check status will no be mantained if the selection changes. Its better to show it checked consulting the data below the ListModel, but then is up to you to implement the method who changes the check status of the data, and notify the change to the JList to be repainted.
I Will post sample code later if you need it
ListCellRenderer

Just implement a ListCellRenderer
public class CheckboxListCellRenderer extends JCheckBox implements ListCellRenderer {
public Component getListCellRendererComponent(JList list, Object value, int index,
boolean isSelected, boolean cellHasFocus) {
setComponentOrientation(list.getComponentOrientation());
setFont(list.getFont());
setBackground(list.getBackground());
setForeground(list.getForeground());
setSelected(isSelected);
setEnabled(list.isEnabled());
setText(value == null ? "" : value.toString());
return this;
}
}
and set the renderer
JList list = new JList();
list.setCellRenderer(new CheckboxListCellRenderer());
this will result in
Details at Custom swing component renderers.
PS: If you want radio elements just replace extends JCheckbox with extends JRadioButton.

I'd probably be looking to use a JTable rather than a JList and since the default rendering of a checkbox is rather ugly, I'd probably be looking to drop in a custom TableModel, CellRenderer and CellEditor to represent a boolean value. Of course, I would imagine this has been done a bajillion times already. Sun has good examples.

Better solution for Java 7 and newer
I stumbled upon this question and realized that some of the answers are pretty old and outdated. Nowadays, JList is generic and thus there are better solutions.
My solution of the generic JCheckBoxList:
import java.awt.Component;
import javax.swing.*;
import javax.swing.border.*;
import java.awt.event.*;
#SuppressWarnings("serial")
public class JCheckBoxList extends JList<JCheckBox> {
protected static Border noFocusBorder = new EmptyBorder(1, 1, 1, 1);
public JCheckBoxList() {
setCellRenderer(new CellRenderer());
addMouseListener(new MouseAdapter() {
public void mousePressed(MouseEvent e) {
int index = locationToIndex(e.getPoint());
if (index != -1) {
JCheckBox checkbox = (JCheckBox) getModel().getElementAt(index);
checkbox.setSelected(!checkbox.isSelected());
repaint();
}
}
});
setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
}
public JCheckBoxList(ListModel<JCheckBox> model){
this();
setModel(model);
}
protected class CellRenderer implements ListCellRenderer<JCheckBox> {
public Component getListCellRendererComponent(
JList<? extends JCheckBox> list, JCheckBox value, int index,
boolean isSelected, boolean cellHasFocus) {
JCheckBox checkbox = value;
//Drawing checkbox, change the appearance here
checkbox.setBackground(isSelected ? getSelectionBackground()
: getBackground());
checkbox.setForeground(isSelected ? getSelectionForeground()
: getForeground());
checkbox.setEnabled(isEnabled());
checkbox.setFont(getFont());
checkbox.setFocusPainted(false);
checkbox.setBorderPainted(true);
checkbox.setBorder(isSelected ? UIManager
.getBorder("List.focusCellHighlightBorder") : noFocusBorder);
return checkbox;
}
}
}
For dynamically adding JCheckBox lists you need to create your own ListModel or add the DefaultListModel.
DefaultListModel<JCheckBox> model = new DefaultListModel<JCheckBox>();
JCheckBoxList checkBoxList = new JCheckBoxList(model);
The DefaultListModel are generic and thus you can use methods specified by JAVA 7 API here like this:
model.addElement(new JCheckBox("Checkbox1"));
model.addElement(new JCheckBox("Checkbox2"));
model.addElement(new JCheckBox("Checkbox3"));

I recommend you use a JPanel with a GridLayout of 1 column. Add the checkBoxes to the JPanel, and set the JPanel as the data source of a JScrollPane. And to get the selected CheckBoxes, just call the getComponents() of the JPanel to get the CheckBoxes.

Odds are good w/ Java that someone has already implemented the widget or utility you need. Part of the benefits of a large OSS community. No need to reinvent the wheel unless you really want to do it yourself. In this case it would be a good learning exercise in CellRenderers and Editors.
My project has had great success with JIDE. The component you want, a Check Box List, is in the JIDE Common Layer (which is OSS and hosted on java.net). The commercial stuff is good too, but you don't need it.
http://www.jidesoft.com/products/oss.htm
https://jide-oss.dev.java.net/

I don't like the solutions that put a Checkbox into the model. The model should only contain data not display elements.
I found this http://www.java2s.com/Tutorials/Java/Swing_How_to/JList/Create_JList_of_CheckBox.htm
which I optimized a bit. The ACTIVE flag represents the Checkbox, the SELECTED flag shows what entry the cursor sits on.
my version requires a renderer
import java.awt.Component;
import javax.swing.JCheckBox;
import javax.swing.JList;
import javax.swing.ListCellRenderer;
class CheckListRenderer extends JCheckBox implements ListCellRenderer<Entity> {
#Override
public Component getListCellRendererComponent(JList<? extends Entity> list,
Entity value, int index, boolean isSelected, boolean cellHasFocus) {
setEnabled(list.isEnabled());
setSelected(value.isActive()); // sets the checkbox
setFont(list.getFont());
if (isSelected) { // highlights the currently selected entry
setBackground(list.getSelectionBackground());
setForeground(list.getSelectionForeground());
} else {
setBackground(list.getBackground());
setForeground(list.getForeground());
}
setText(value.toString()+" - A" + value.isActive()+" - F"+cellHasFocus+" - S"+isSelected );
return this;
}
}
and an entity that got the active field:
public class Entity {
private boolean active = true;
public boolean isActive() {
return active;
}
public void setActive(boolean isActive) {
this.active = isActive;
}
}
Now you only have to add this to your JList:
list = new JList<Entity>();
list.setModel(new DefaultListModel<Entity>());
list.setCellRenderer(new CheckListRenderer());
list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
list.addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent event) {
if (event.getX() < 20) {
// Quick and dirty: only change the tick if clicked into the leftmost pixels
#SuppressWarnings("unchecked")
JList<Entity> list = ((JList<Entity>) event.getSource());
int index = list.locationToIndex(event.getPoint());// Get index of item clicked
if (index >= 0) {
Entity item = (Entity) list.getModel().getElementAt(index);
item.setActive(!item.isActive()); // Toggle selected state
list.repaint(list.getCellBounds(index, index));// Repaint cell
}
}
}
});

All of the aggregate components in Swing--that is, components made up other components, such as JTable, JTree, or JComboBox--can be highly customized. For example, a JTable component normally displays a grid of JLabel components, but it can also display JButtons, JTextFields, or even other JTables. Getting these aggregate components to display non-default objects is the easy part, however. Making them respond properly to keyboard and mouse events is a much harder task, due to Swing's separation of components into "renderers" and "editors." This separation was (in my opinion) a poor design choice and only serves to complicate matters when trying to extend Swing components.
To see what I mean, try enhancing Swing's JList component so that it displays checkboxes instead of labels. According to Swing philosophy, this task requires implementing two interfaces: ListCellRenderer (for drawing the checkboxes) and CellEditor (for handling keyboard and mouse events on the checkboxes). Implementing the ListCellRenderer interface is easy enough, but the CellEditor interface can be rather clumsy and hard to understand. In this particular case, I would suggest forgetting CellEditor entirely and to handle input events directly, as shown in the following code.
import javax.swing.*;
import javax.swing.border.*;
import java.awt.*;
import java.awt.event.*;
public class CheckBoxList extends JList
{
protected static Border noFocusBorder = new EmptyBorder(1, 1, 1, 1);
public CheckBoxList()
{
setCellRenderer(new CellRenderer());
addMouseListener(new MouseAdapter()
{
public void mousePressed(MouseEvent e)
{
int index = locationToIndex(e.getPoint());
if (index != -1) {
JCheckBox checkbox = (JCheckBox)
getModel().getElementAt(index);
checkbox.setSelected(
!checkbox.isSelected());
repaint();
}
}
}
);
setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
}
protected class CellRenderer implements ListCellRenderer
{
public Component getListCellRendererComponent(
JList list, Object value, int index,
boolean isSelected, boolean cellHasFocus)
{
JCheckBox checkbox = (JCheckBox) value;
checkbox.setBackground(isSelected ?
getSelectionBackground() : getBackground());
checkbox.setForeground(isSelected ?
getSelectionForeground() : getForeground());
checkbox.setEnabled(isEnabled());
checkbox.setFont(getFont());
checkbox.setFocusPainted(false);
checkbox.setBorderPainted(true);
checkbox.setBorder(isSelected ?
UIManager.getBorder(
"List.focusCellHighlightBorder") : noFocusBorder);
return checkbox;
}
}
}
Here, I intercept mouse clicks from the listbox and simulate a click on the appropriate checkbox. The result is a "CheckBoxList" component that is both simpler and smaller than an equivalent component using the CellEditor interface. To use the class, simply instantiate it, then pass it an array of JCheckBox objects (or subclasses of JCheckBox objects) by calling setListData. Note that the checkboxes in this component will not respond to keypresses (i.e. the spacebar), but you could always add your own key listener if needed.
Source: DevX.com

Here is just a little addition to the JCheckBoxList by Rawa. This will add the ability to select using space bar. If multiple items are selected, all will be set to inverted value of the first item.
addKeyListener(new KeyAdapter() {
#Override
public void keyPressed(KeyEvent e) {
int index = getSelectedIndex();
if (index != -1 && e.getKeyCode() == KeyEvent.VK_SPACE) {
boolean newVal = !((JCheckBox) (getModel()
.getElementAt(index))).isSelected();
for (int i : getSelectedIndices()) {
JCheckBox checkbox = (JCheckBox) getModel()
.getElementAt(i);
checkbox.setSelected(newVal);
repaint();
}
}
}
});

this is yet another example of making list with checkboxes
class JCheckList<T> extends JList<T> {
protected static Border noFocusBorder = new EmptyBorder(1, 1, 1, 1);
public void setSelected(int index) {
if (index != -1) {
JCheckBox checkbox = (JCheckBox) getModel().getElementAt(index);
checkbox.setSelected(
!checkbox.isSelected());
repaint();
}
}
protected static class CellListener
extends DefaultListModel
implements ListDataListener {
ListModel ls;
public CellListener(ListModel ls) {
ls.addListDataListener(this);
int i = ls.getSize();
for (int v = 0; v < i; v++) {
var r = new JCheckBox();
r.setText(ls.getElementAt(v).toString());
this.addElement(r);
}
this.ls = ls;
}
#Override
public void intervalAdded(ListDataEvent e) {
int begin = e.getIndex0();
int end = e.getIndex1();
for (; begin <= end; begin++) {
var r = new JCheckBox();
r.setText(ls.getElementAt(begin).toString());
this.add(begin, r);
}
}
#Override
public void intervalRemoved(ListDataEvent e) {
int begin = e.getIndex0();
int end = e.getIndex1();
for (; begin <= end; end--) {
this.remove(begin);
}
}
#Override
public void contentsChanged(ListDataEvent e) {
}
}
public JCheckList() {
setCellRenderer(new CellRenderer());
addMouseListener(new MouseAdapter() {
public void mousePressed(MouseEvent e) {
int index = locationToIndex(e.getPoint());
setSelected(index);
}
}
);
addKeyListener(new KeyListener(){
#Override
public void keyTyped(KeyEvent e) {
}
#Override
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_SPACE){
int index = JCheckList.this.getSelectedIndex();
setSelected(index);
}
}
#Override
public void keyReleased(KeyEvent e) {
}
});
setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
}
#Override
public void setModel(ListModel<T> d) {
var r = new CellListener(d);
d.addListDataListener(r);
super.setModel(r);
}
protected class CellRenderer implements ListCellRenderer {
public Component getListCellRendererComponent(
JList list, Object value, int index,
boolean isSelected, boolean cellHasFocus) {
JCheckBox checkbox = (JCheckBox) value;
checkbox.setBackground(isSelected
? getSelectionBackground() : getBackground());
checkbox.setForeground(isSelected
? getSelectionForeground() : getForeground());
checkbox.setEnabled(isEnabled());
checkbox.setFont(getFont());
checkbox.setFocusPainted(false);
checkbox.setBorderPainted(true);
checkbox.setBorder(isSelected
? UIManager.getBorder(
"List.focusCellHighlightBorder") : noFocusBorder);
return checkbox;
}
}
}