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25 
26 package javax.swing.undo;
27 
28 import java.io.Serializable;
29 import javax.swing.UIManager;
30 
31 /**
32  * An abstract implementation of <code>UndoableEdit</code>,
33  * implementing simple responses to all boolean methods in
34  * that interface.
35  *
36  * @author Ray Ryan
37  */
38 @SuppressWarnings("serial") // Same-version serialization only
39 public class AbstractUndoableEdit implements UndoableEdit, Serializable {
40 
41     /**
42      * String returned by <code>getUndoPresentationName</code>;
43      * as of Java 2 platform v1.3.1 this field is no longer used. This value
44      * is now localized and comes from the defaults table with key
45      * <code>AbstractUndoableEdit.undoText</code>.
46      *
47      * @see javax.swing.UIDefaults
48      */
49     protected static final String UndoName = "Undo";
50 
51     /**
52      * String returned by <code>getRedoPresentationName</code>;
53      * as of Java 2 platform v1.3.1 this field is no longer used. This value
54      * is now localized and comes from the defaults table with key
55      * <code>AbstractUndoableEdit.redoText</code>.
56      *
57      * @see javax.swing.UIDefaults
58      */
59     protected static final String RedoName = "Redo";
60 
61     /**
62      * Defaults to true; becomes false if this edit is undone, true
63      * again if it is redone.
64      */
65     boolean hasBeenDone;
66 
67     /**
68      * True if this edit has not received <code>die</code>; defaults
69      * to <code>true</code>.
70      */
71     boolean alive;
72 
73     /**
74      * Creates an <code>AbstractUndoableEdit</code> which defaults
75      * <code>hasBeenDone</code> and <code>alive</code> to <code>true</code>.
76      */
AbstractUndoableEdit()77     public AbstractUndoableEdit() {
78         super();
79 
80         hasBeenDone = true;
81         alive = true;
82     }
83 
84     /**
85      * Sets <code>alive</code> to false. Note that this
86      * is a one way operation; dead edits cannot be resurrected.
87      * Sending <code>undo</code> or <code>redo</code> to
88      * a dead edit results in an exception being thrown.
89      *
90      * <p>Typically an edit is killed when it is consolidated by
91      * another edit's <code>addEdit</code> or <code>replaceEdit</code>
92      * method, or when it is dequeued from an <code>UndoManager</code>.
93      */
die()94     public void die() {
95         alive = false;
96     }
97 
98     /**
99      * Throws <code>CannotUndoException</code> if <code>canUndo</code>
100      * returns <code>false</code>. Sets <code>hasBeenDone</code>
101      * to <code>false</code>. Subclasses should override to undo the
102      * operation represented by this edit. Override should begin with
103      * a call to super.
104      *
105      * @exception CannotUndoException if <code>canUndo</code>
106      *    returns <code>false</code>
107      * @see     #canUndo
108      */
undo()109     public void undo() throws CannotUndoException {
110         if (!canUndo()) {
111             throw new CannotUndoException();
112         }
113         hasBeenDone = false;
114     }
115 
116     /**
117      * Returns true if this edit is <code>alive</code>
118      * and <code>hasBeenDone</code> is <code>true</code>.
119      *
120      * @return true if this edit is <code>alive</code>
121      *    and <code>hasBeenDone</code> is <code>true</code>
122      *
123      * @see     #die
124      * @see     #undo
125      * @see     #redo
126      */
canUndo()127     public boolean canUndo() {
128         return alive && hasBeenDone;
129     }
130 
131     /**
132      * Throws <code>CannotRedoException</code> if <code>canRedo</code>
133      * returns false. Sets <code>hasBeenDone</code> to <code>true</code>.
134      * Subclasses should override to redo the operation represented by
135      * this edit. Override should begin with a call to super.
136      *
137      * @exception CannotRedoException if <code>canRedo</code>
138      *     returns <code>false</code>
139      * @see     #canRedo
140      */
redo()141     public void redo() throws CannotRedoException {
142         if (!canRedo()) {
143             throw new CannotRedoException();
144         }
145         hasBeenDone = true;
146     }
147 
148     /**
149      * Returns <code>true</code> if this edit is <code>alive</code>
150      * and <code>hasBeenDone</code> is <code>false</code>.
151      *
152      * @return <code>true</code> if this edit is <code>alive</code>
153      *   and <code>hasBeenDone</code> is <code>false</code>
154      * @see     #die
155      * @see     #undo
156      * @see     #redo
157      */
canRedo()158     public boolean canRedo() {
159         return alive && !hasBeenDone;
160     }
161 
162     /**
163      * This default implementation returns false.
164      *
165      * @param anEdit the edit to be added
166      * @return false
167      *
168      * @see UndoableEdit#addEdit
169      */
addEdit(UndoableEdit anEdit)170     public boolean addEdit(UndoableEdit anEdit) {
171         return false;
172     }
173 
174     /**
175      * This default implementation returns false.
176      *
177      * @param anEdit the edit to replace
178      * @return false
179      *
180      * @see UndoableEdit#replaceEdit
181      */
replaceEdit(UndoableEdit anEdit)182     public boolean replaceEdit(UndoableEdit anEdit) {
183         return false;
184     }
185 
186     /**
187      * This default implementation returns true.
188      *
189      * @return true
190      * @see UndoableEdit#isSignificant
191      */
isSignificant()192     public boolean isSignificant() {
193         return true;
194     }
195 
196     /**
197      * This default implementation returns "". Used by
198      * <code>getUndoPresentationName</code> and
199      * <code>getRedoPresentationName</code> to
200      * construct the strings they return. Subclasses should override to
201      * return an appropriate description of the operation this edit
202      * represents.
203      *
204      * @return the empty string ""
205      *
206      * @see     #getUndoPresentationName
207      * @see     #getRedoPresentationName
208      */
getPresentationName()209     public String getPresentationName() {
210         return "";
211     }
212 
213     /**
214      * Retreives the value from the defaults table with key
215      * <code>AbstractUndoableEdit.undoText</code> and returns
216      * that value followed by a space, followed by
217      * <code>getPresentationName</code>.
218      * If <code>getPresentationName</code> returns "",
219      * then the defaults value is returned alone.
220      *
221      * @return the value from the defaults table with key
222      *    <code>AbstractUndoableEdit.undoText</code>, followed
223      *    by a space, followed by <code>getPresentationName</code>
224      *    unless <code>getPresentationName</code> is "" in which
225      *    case, the defaults value is returned alone.
226      * @see #getPresentationName
227      */
getUndoPresentationName()228     public String getUndoPresentationName() {
229         String name = getPresentationName();
230         if (!"".equals(name)) {
231             name = UIManager.getString("AbstractUndoableEdit.undoText") +
232                 " " + name;
233         } else {
234             name = UIManager.getString("AbstractUndoableEdit.undoText");
235         }
236 
237         return name;
238     }
239 
240     /**
241      * Retreives the value from the defaults table with key
242      * <code>AbstractUndoableEdit.redoText</code> and returns
243      * that value followed by a space, followed by
244      * <code>getPresentationName</code>.
245      * If <code>getPresentationName</code> returns "",
246      * then the defaults value is returned alone.
247      *
248      * @return the value from the defaults table with key
249      *    <code>AbstractUndoableEdit.redoText</code>, followed
250      *    by a space, followed by <code>getPresentationName</code>
251      *    unless <code>getPresentationName</code> is "" in which
252      *    case, the defaults value is returned alone.
253      * @see #getPresentationName
254      */
getRedoPresentationName()255     public String getRedoPresentationName() {
256         String name = getPresentationName();
257         if (!"".equals(name)) {
258             name = UIManager.getString("AbstractUndoableEdit.redoText") +
259                 " " + name;
260         } else {
261             name = UIManager.getString("AbstractUndoableEdit.redoText");
262         }
263 
264         return name;
265     }
266 
267     /**
268      * Returns a string that displays and identifies this
269      * object's properties.
270      *
271      * @return a String representation of this object
272      */
toString()273     public String toString()
274     {
275         return super.toString()
276             + " hasBeenDone: " + hasBeenDone
277             + " alive: " + alive;
278     }
279 }
280