مساعدة فى ال undo,redo

انا اسخدمت ال

text.getDocument().addUndoableEditListener(new MyUndoableEditListener());

فى عمل ال undo ,redo

و ال class

class MyUndoabelListener implements UndoableEditListener
        {
			public void undoableEditHappened(UndoableEditEvent e){
				//Remember the edit and update the menus
				undo.addEdit(e.getEdit());
				undoAction.update();
				redoAction.update();
			}
		}

ولكن دائما يطلع الخطا

C:Documents and SettingsahmedDesktopPadCopy of new stylenotePad.java:138: cannot resolve symbol
symbol  : class UndoableEditListener 
location: class notePad.MyUndoabelListener
 class MyUndoabelListener implements UndoableEditListener
                                     ^
C:Documents and SettingsahmedDesktopPadCopy of new stylenotePad.java:140: cannot resolve symbol
symbol  : class UndoableEditEvent 
location: class notePad.MyUndoabelListener
			public void undoableEditHappened(UndoableEditEvent e){
                                                         ^
C:Documents and SettingsahmedDesktopPadCopy of new stylenotePad.java:129: cannot resolve symbol
symbol  : class MyUndoableEditListener 
location: class notePad
        text.getDocument().addUndoableEditListener(new MyUndoableEditListener());
                                                       ^
3 errors

Tool completed with exit code 1

ارجو الافادة؟؟؟؟؟