Currently, neither ButtonGroup or JButtonGroup allows you to unselect all buttons. I have modified Daniel's code to provide this functionality. Here's the new class:

public class JButtonGroup extends ButtonGroup {
/**
* Used to deselect all buttons in the group
*/
private static final AbstractButton dummyButton = new JButton();
/**
* Stores a reference to the currently selected button in the group
*/
private AbstractButton selectedButton;

/**
* Creates an empty <code>JButtonGroup</code>
*/
public JButtonGroup() {
super();
add(dummyButton);
}

/**
* Creates a <code>JButtonGroup</code> object from an array of buttons and adds the buttons to the group
* No button will be selected initially.
* @param buttons an array of <code>AbstractButton</code>s
*/
public JButtonGroup(AbstractButton[] buttons) {
add(buttons);
add(dummyButton);
}

/**
* Adds a button to the group
* @param button an <code>AbstractButton</code> reference
*/
public void add(AbstractButton button) {
if (button == null || buttons.contains(button)) {
return;
}
super.add(button);
if (getSelection() == button.getModel()) {
selectedButton = button;
}
}

/**
* Adds an array of buttons to the group
* @param buttons an array of <code>AbstractButton</code>s
*/
public void add(AbstractButton[] buttons) {
if (buttons == null) {
return;
}
for (int i=0; i<buttons.length; i++) {
add(buttons);
}
}

/**
* Removes a button from the group
* @param button the button to be removed
*/
public void remove(AbstractButton button) {
if (button != null) {
if (selectedButton == button) {
selectedButton = null;
}
super.remove(button);
}
}

/**
* Removes all the buttons in the array from the group
* @param buttons an array of <code>AbstractButton</code>s
*/
public void remove(AbstractButton[] buttons) {
if (buttons == null) {
return;
}
for (int i=0; i<buttons.length; i++) {
remove(buttons);
}
}

/**
* Sets the selected button in the group
* Only one button in the group can be selected
* @param button an <code>AbstractButton</code> reference
* @param selected an <code>boolean</code> representing the selection state of the button
*/
public void setSelected(AbstractButton button, boolean selected) {
if (button != null && buttons.contains(button)) {
setSelected(button.getModel(), selected);
if (getSelection() == button.getModel()) {
selectedButton = button;
}
}
}

/**
* Sets the selected button model in the group
* @param model a <code>ButtonModel</code> reference
* @param selected an <code>boolean</code> representing the selection state of the button
*/
public void setSelected(ButtonModel model, boolean selected) {
AbstractButton button = getButton(model);
if (buttons.contains(button)) {
super.setSelected(model, selected);
if(model != dummyButton.getModel()) {
selectedButton = button;
}
}
}

/**
* Returns the <code>AbstractButton</code> whose <code>ButtonModel</code> is given.
* If the model does not belong to a button in the group, returns null.
* @param model a <code>ButtonModel</code> that should belong to a button in the group
* @return an <code>AbstractButton</code> reference whose model is <code>model</code> if the button belongs to the group, <code>null</code>otherwise
*/
public AbstractButton getButton(ButtonModel model) {
for(Iterator i = buttons.iterator(); i.hasNext(); ) {
AbstractButton ab = (AbstractButton)i.next();
if (ab.getModel() == model) {
return ab;
}
}
return null;
}

/**
* Returns the selected button in the group.
* @return a reference to the currently selected button in the group or <code>null</code> if no button is selected
*/
public AbstractButton getSelected() {
if(selectedButton == dummyButton) {
return null;
} else {
return selectedButton;
}
}

public ButtonModel getSelection() {
if(selectedButton == dummyButton) {
return null;
} else {
return super.getSelection();
}
}

/**
* Returns whether the button is selected
* @param button an <code>AbstractButton</code> reference
* @return <code>true</code> if the button is selected, <code>false</code> otherwise
*/
public boolean isSelected(AbstractButton button) {
if(button == dummyButton) {
return false;
}
return button == selectedButton;
}

/**
* Returns the buttons in the group as a <code>List</code>
* @return a <code>List</code> containing the buttons in the group, in the order they were added to the group
*/
public List getButtons() {
List allButtons = new LinkedList(buttons);
allButtons.remove(dummyButton);
return Collections.unmodifiableList(allButtons);
}

/**
* Checks whether the group contains the given button
* @return <code>true</code> if the button is contained in the group, <code>false</code> otherwise
*/
public boolean contains(AbstractButton button) {
if(button == dummyButton) {
return false;
}
return buttons.contains(button);
}

/**
* unselects all buttons
*/
public void unselectAll() {
setSelected(dummyButton, true);
}
}

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