/* * Copyright (c) 1997, 2008, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation.  Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */package javax.swing; import java.awt.event.*;import java.util.Vector;import java.util.Enumeration;import java.io.Serializable; /** * This class is used to create a multiple-exclusion scope for * a set of buttons. Creating a set of buttons with the * same <code>ButtonGroup</code> object means that * turning "on" one of those buttons * turns off all other buttons in the group. * <p> * A <code>ButtonGroup</code> can be used with * any set of objects that inherit from <code>AbstractButton</code>. * Typically a button group contains instances of * <code>JRadioButton</code>, * <code>JRadioButtonMenuItem</code>, * or <code>JToggleButton</code>. * It wouldn't make sense to put an instance of * <code>JButton</code> or <code>JMenuItem</code> * in a button group * because <code>JButton</code> and <code>JMenuItem</code> * don't implement the selected state. * <p> * Initially, all buttons in the group are unselected. * <p> * For examples and further information on using button groups see * <a href="http://java.sun.com/docs/books/tutorial/uiswing/components/button.html#radiobutton">How to Use Radio Buttons</a>, * a section in <em>The Java Tutorial</em>. * <p> * <strong>Warning:</strong> * 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 JavaBeans<sup><font size="-2">TM</font></sup> * has been added to the <code>java.beans</code> package. * Please see {@link java.beans.XMLEncoder}. * * @author Jeff Dinkins */public class ButtonGroup implements Serializable {     // the list of buttons participating in this group    protected Vector<AbstractButton> buttons = new Vector<AbstractButton>();     /**     * The current selection.     */    ButtonModel selection = null;     /**     * Creates a new <code>ButtonGroup</code>.     */    public ButtonGroup() {}     /**     * Adds the button to the group.     * @param b the button to be added     */    public void add(AbstractButton b) {        if(b == null) {            return;        }        buttons.addElement(b);         if (b.isSelected()) {            if (selection == null) {                selection = b.getModel();            } else {                b.setSelected(false);            }        }         b.getModel().setGroup(this);    }     /**     * Removes the button from the group.     * @param b the button to be removed     */    public void remove(AbstractButton b) {        if(b == null) {            return;        }        buttons.removeElement(b);        if(b.getModel() == selection) {            selection = null;        }        b.getModel().setGroup(null);    }     /**     * Clears the selection such that none of the buttons     * in the <code>ButtonGroup</code> are selected.     *     * @since 1.6     */    public void clearSelection() {        if (selection != null) {            ButtonModel oldSelection = selection;            selection = null;            oldSelection.setSelected(false);        }    }     /**     * Returns all the buttons that are participating in     * this group.     * @return an <code>Enumeration</code> of the buttons in this group     */    public Enumeration<AbstractButton> getElements() {        return buttons.elements();    }     /**     * Returns the model of the selected button.     * @return the selected button model     */    public ButtonModel getSelection() {        return selection;    }     /**     * Sets the selected value for the <code>ButtonModel</code>.     * Only one button in the group may be selected at a time.     * @param m the <code>ButtonModel</code>     * @param b <code>true</code> if this button is to be     *   selected, otherwise <code>false</code>     */    public void setSelected(ButtonModel m, boolean b) {        if (b && m != null && m != selection) {            ButtonModel oldSelection = selection;            selection = m;            if (oldSelection != null) {                oldSelection.setSelected(false);            }            m.setSelected(true);        }    }     /**     * Returns whether a <code>ButtonModel</code> is selected.     * @return <code>true</code> if the button is selected,     *   otherwise returns <code>false</code>     */    public boolean isSelected(ButtonModel m) {        return (m == selection);    }     /**     * Returns the number of buttons in the group.     * @return the button count     * @since 1.3     */    public int getButtonCount() {        if (buttons == null) {            return 0;        } else {            return buttons.size();        }    } }