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	/*
	* 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.undo;

	import javax.swing.event.*;
	import java.util.*;

	/**
	* A support class used for managing <code>UndoableEdit</code> listeners.
	*
	* @author Ray Ryan
	*/
	public class UndoableEditSupport {
	protected int updateLevel;
	protected CompoundEdit compoundEdit;
	protected Vector<UndoableEditListener> listeners;
	protected Object realSource;

	/**
	* Constructs an <code>UndoableEditSupport</code> object.
	*/
	public UndoableEditSupport() {
	this(null);
	}

	/**
	* Constructs an <code>UndoableEditSupport</code> object.
	*
	* @param r an <code>Object</code>
	*/
	public UndoableEditSupport(Object r) {
	realSource = r == null ? this : r;
	updateLevel = 0;
	compoundEdit = null;
	listeners = new Vector<UndoableEditListener>();
	}

	/**
	* Registers an <code>UndoableEditListener</code>.
	* The listener is notified whenever an edit occurs which can be undone.
	*
	* @param l an <code>UndoableEditListener</code> object
	* @see #removeUndoableEditListener
	*/
	public synchronized void addUndoableEditListener(UndoableEditListener l) {
	listeners.addElement(l);
	}

	/**
	* Removes an <code>UndoableEditListener</code>.
	*
	* @param l the <code>UndoableEditListener</code> object to be removed
	* @see #addUndoableEditListener
	*/
	public synchronized void removeUndoableEditListener(UndoableEditListener l)
	{
	listeners.removeElement(l);
	}

	/**
	* Returns an array of all the <code>UndoableEditListener</code>s added
	* to this UndoableEditSupport with addUndoableEditListener().
	*
	* @return all of the <code>UndoableEditListener</code>s added or an empty
	* array if no listeners have been added
	* @since 1.4
	*/
	public synchronized UndoableEditListener[] getUndoableEditListeners() {
	return listeners.toArray(new UndoableEditListener[0]);
	}

	/**
	* Called only from <code>postEdit</code> and <code>endUpdate</code>. Calls
	* <code>undoableEditHappened</code> in all listeners. No synchronization
	* is performed here, since the two calling methods are synchronized.
	*/
	protected void _postEdit(UndoableEdit e) {
	UndoableEditEvent ev = new UndoableEditEvent(realSource, e);
	Enumeration cursor = ((Vector)listeners.clone()).elements();
	while (cursor.hasMoreElements()) {
	((UndoableEditListener)cursor.nextElement()).
	undoableEditHappened(ev);
	}
	}

	/**
	* DEADLOCK WARNING: Calling this method may call
	* <code>undoableEditHappened</code> in all listeners.
	* It is unwise to call this method from one of its listeners.
	*/
	public synchronized void postEdit(UndoableEdit e) {
	if (updateLevel == 0) {
	_postEdit(e);
	} else {
	// PENDING(rjrjr) Throw an exception if this fails?
	compoundEdit.addEdit(e);
	}
	}

	/**
	* Returns the update level value.
	*
	* @return an integer representing the update level
	*/
	public int getUpdateLevel() {
	return updateLevel;
	}

	/**
	*
	*/
	public synchronized void beginUpdate() {
	if (updateLevel == 0) {
	compoundEdit = createCompoundEdit();
	}
	updateLevel++;
	}

	/**
	* Called only from <code>beginUpdate</code>.
	* Exposed here for subclasses' use.
	*/
	protected CompoundEdit createCompoundEdit() {
	return new CompoundEdit();
	}

	/**
	* DEADLOCK WARNING: Calling this method may call
	* <code>undoableEditHappened</code> in all listeners.
	* It is unwise to call this method from one of its listeners.
	*/
	public synchronized void endUpdate() {
	updateLevel--;
	if (updateLevel == 0) {
	compoundEdit.end();
	_postEdit(compoundEdit);
	compoundEdit = null;
	}
	}

	/**
	* Returns a string that displays and identifies this
	* object's properties.
	*
	* @return a <code>String</code> representation of this object
	*/
	public String toString() {
	return super.toString() +
	" updateLevel: " + updateLevel +
	" listeners: " + listeners +
	" compoundEdit: " + compoundEdit;
	}
	}

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