JavaTM 2 Platform
Standard Ed. 5.0

Class ButtonGroup

  extended by javax.swing.ButtonGroup
All Implemented Interfaces:

public class ButtonGroup
extends Object
implements Serializable

This class is used to create a multiple-exclusion scope for a set of buttons. Creating a set of buttons with the same ButtonGroup object means that turning "on" one of those buttons turns off all other buttons in the group.

A ButtonGroup can be used with any set of objects that inherit from AbstractButton. Typically a button group contains instances of JRadioButton, JRadioButtonMenuItem, or JToggleButton. It wouldn't make sense to put an instance of JButton or JMenuItem in a button group because JButton and JMenuItem don't implement the selected state.

Initially, all buttons in the group are unselected. Once any button is selected, one button is always selected in the group. There is no way to turn a button programmatically to "off", in order to clear the button group. To give the appearance of "none selected", add an invisible radio button to the group and then programmatically select that button to turn off all the displayed radio buttons. For example, a normal button with the label "none" could be wired to select the invisible radio button.

For examples and further information on using button groups see How to Use Radio Buttons, a section in The Java Tutorial.

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeansTM has been added to the java.beans package. Please see XMLEncoder.

Field Summary
protected  Vector<AbstractButton> buttons
Constructor Summary
          Creates a new ButtonGroup.
Method Summary
 void add(AbstractButton b)
          Adds the button to the group.
 int getButtonCount()
          Returns the number of buttons in the group.
 Enumeration<AbstractButton> getElements()
          Returns all the buttons that are participating in this group.
 ButtonModel getSelection()
          Returns the model of the selected button.
 boolean isSelected(ButtonModel m)
          Returns whether a ButtonModel is selected.
 void remove(AbstractButton b)
          Removes the button from the group.
 void setSelected(ButtonModel m, boolean b)
          Sets the selected value for the ButtonModel.
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail


protected Vector<AbstractButton> buttons
Constructor Detail


public ButtonGroup()
Creates a new ButtonGroup.

Method Detail


public void add(AbstractButton b)
Adds the button to the group.

b - the button to be added


public void remove(AbstractButton b)
Removes the button from the group.

b - the button to be removed


public Enumeration<AbstractButton> getElements()
Returns all the buttons that are participating in this group.

an Enumeration of the buttons in this group


public ButtonModel getSelection()
Returns the model of the selected button.

the selected button model


public void setSelected(ButtonModel m,
                        boolean b)
Sets the selected value for the ButtonModel. Only one button in the group may be selected at a time.

m - the ButtonModel
b - true if this button is to be selected, otherwise false


public boolean isSelected(ButtonModel m)
Returns whether a ButtonModel is selected.

true if the button is selected, otherwise returns false


public int getButtonCount()
Returns the number of buttons in the group.

the button count

JavaTM 2 Platform
Standard Ed. 5.0

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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Copyright 2004 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.