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	/*
	* Copyright (c) 1997, 2006, 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 java.io.Serializable;
	import javax.swing.UIManager;

	/**
	* An abstract implementation of <code>UndoableEdit</code>,
	* implementing simple responses to all boolean methods in
	* that interface.
	*
	* @author Ray Ryan
	*/
	public class AbstractUndoableEdit implements UndoableEdit, Serializable {

	/**
	* String returned by <code>getUndoPresentationName</code>;
	* as of Java 2 platform v1.3.1 this field is no longer used. This value
	* is now localized and comes from the defaults table with key
	* <code>AbstractUndoableEdit.undoText</code>.
	*
	* @see javax.swing.UIDefaults
	*/
	protected static final String UndoName = "Undo";

	/**
	* String returned by <code>getRedoPresentationName</code>;
	* as of Java 2 platform v1.3.1 this field is no longer used. This value
	* is now localized and comes from the defaults table with key
	* <code>AbstractUndoableEdit.redoText</code>.
	*
	* @see javax.swing.UIDefaults
	*/
	protected static final String RedoName = "Redo";

	/**
	* Defaults to true; becomes false if this edit is undone, true
	* again if it is redone.
	*/
	boolean hasBeenDone;

	/**
	* True if this edit has not received <code>die</code>; defaults
	* to <code>true</code>.
	*/
	boolean alive;

	/**
	* Creates an <code>AbstractUndoableEdit</code> which defaults
	* <code>hasBeenDone</code> and <code>alive</code> to <code>true</code>.
	*/
	public AbstractUndoableEdit() {
	super();

	hasBeenDone = true;
	alive = true;
	}

	/**
	* Sets <code>alive</code> to false. Note that this
	* is a one way operation; dead edits cannot be resurrected.
	* Sending <code>undo</code> or <code>redo</code> to
	* a dead edit results in an exception being thrown.
	*
	* <p>Typically an edit is killed when it is consolidated by
	* another edit's <code>addEdit</code> or <code>replaceEdit</code>
	* method, or when it is dequeued from an <code>UndoManager</code>.
	*/
	public void die() {
	alive = false;
	}

	/**
	* Throws <code>CannotUndoException</code> if <code>canUndo</code>
	* returns <code>false</code>. Sets <code>hasBeenDone</code>
	* to <code>false</code>. Subclasses should override to undo the
	* operation represented by this edit. Override should begin with
	* a call to super.
	*
	* @exception CannotUndoException if <code>canUndo</code>
	* returns <code>false</code>
	* @see #canUndo
	*/
	public void undo() throws CannotUndoException {
	if (!canUndo()) {
	throw new CannotUndoException();
	}
	hasBeenDone = false;
	}

	/**
	* Returns true if this edit is <code>alive</code>
	* and <code>hasBeenDone</code> is <code>true</code>.
	*
	* @return true if this edit is <code>alive</code>
	* and <code>hasBeenDone</code> is <code>true</code>
	*
	* @see #die
	* @see #undo
	* @see #redo
	*/
	public boolean canUndo() {
	return alive && hasBeenDone;
	}

	/**
	* Throws <code>CannotRedoException</code> if <code>canRedo</code>
	* returns false. Sets <code>hasBeenDone</code> to <code>true</code>.
	* Subclasses should override to redo the operation represented by
	* this edit. Override should begin with a call to super.
	*
	* @exception CannotRedoException if <code>canRedo</code>
	* returns <code>false</code>
	* @see #canRedo
	*/
	public void redo() throws CannotRedoException {
	if (!canRedo()) {
	throw new CannotRedoException();
	}
	hasBeenDone = true;
	}

	/**
	* Returns <code>true</code> if this edit is <code>alive</code>
	* and <code>hasBeenDone</code> is <code>false</code>.
	*
	* @return <code>true</code> if this edit is <code>alive</code>
	* and <code>hasBeenDone</code> is <code>false</code>
	* @see #die
	* @see #undo
	* @see #redo
	*/
	public boolean canRedo() {
	return alive && !hasBeenDone;
	}

	/**
	* This default implementation returns false.
	*
	* @param anEdit the edit to be added
	* @return false
	*
	* @see UndoableEdit#addEdit
	*/
	public boolean addEdit(UndoableEdit anEdit) {
	return false;
	}

	/**
	* This default implementation returns false.
	*
	* @param anEdit the edit to replace
	* @return false
	*
	* @see UndoableEdit#replaceEdit
	*/
	public boolean replaceEdit(UndoableEdit anEdit) {
	return false;
	}

	/**
	* This default implementation returns true.
	*
	* @return true
	* @see UndoableEdit#isSignificant
	*/
	public boolean isSignificant() {
	return true;
	}

	/**
	* This default implementation returns "". Used by
	* <code>getUndoPresentationName</code> and
	* <code>getRedoPresentationName</code> to
	* construct the strings they return. Subclasses should override to
	* return an appropriate description of the operation this edit
	* represents.
	*
	* @return the empty string ""
	*
	* @see #getUndoPresentationName
	* @see #getRedoPresentationName
	*/
	public String getPresentationName() {
	return "";
	}

	/**
	* Retreives the value from the defaults table with key
	* <code>AbstractUndoableEdit.undoText</code> and returns
	* that value followed by a space, followed by
	* <code>getPresentationName</code>.
	* If <code>getPresentationName</code> returns "",
	* then the defaults value is returned alone.
	*
	* @return the value from the defaults table with key
	* <code>AbstractUndoableEdit.undoText</code>, followed
	* by a space, followed by <code>getPresentationName</code>
	* unless <code>getPresentationName</code> is "" in which
	* case, the defaults value is returned alone.
	* @see #getPresentationName
	*/
	public String getUndoPresentationName() {
	String name = getPresentationName();
	if (!"".equals(name)) {
	name = UIManager.getString("AbstractUndoableEdit.undoText") +
	" " + name;
	} else {
	name = UIManager.getString("AbstractUndoableEdit.undoText");
	}

	return name;
	}

	/**
	* Retreives the value from the defaults table with key
	* <code>AbstractUndoableEdit.redoText</code> and returns
	* that value followed by a space, followed by
	* <code>getPresentationName</code>.
	* If <code>getPresentationName</code> returns "",
	* then the defaults value is returned alone.
	*
	* @return the value from the defaults table with key
	* <code>AbstractUndoableEdit.redoText</code>, followed
	* by a space, followed by <code>getPresentationName</code>
	* unless <code>getPresentationName</code> is "" in which
	* case, the defaults value is returned alone.
	* @see #getPresentationName
	*/
	public String getRedoPresentationName() {
	String name = getPresentationName();
	if (!"".equals(name)) {
	name = UIManager.getString("AbstractUndoableEdit.redoText") +
	" " + name;
	} else {
	name = UIManager.getString("AbstractUndoableEdit.redoText");
	}

	return name;
	}

	/**
	* Returns a string that displays and identifies this
	* object's properties.
	*
	* @return a String representation of this object
	*/
	public String toString()
	{
	return super.toString()
	+ " hasBeenDone: " + hasBeenDone
	+ " alive: " + alive;
	}
	}

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