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	/*
	* Copyright (c) 1997, 2013, 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="https://docs.oracle.com/javase/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™
	* has been added to the <code>java.beans</code> package.
	* Please see {@link java.beans.XMLEncoder}.
	*
	* @author Jeff Dinkins
	*/
	@SuppressWarnings("serial")
	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();
	}
	}

	}

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