Java Foundation Classes in a Nutshell

CHAPTER 35

Thejavax.swing.undo Package

The classes and interfaces in this package form the undo framework for Swing

applications. The UndoManager manages a list of UndoableEdit objects, each of which

can be individually undone or redone. Any Swing application that wants to pro-

vide an undo capability will find this package useful. Figure 35-1 shows the class

hierarchy of this package.

extends implements

INTERFACE

KEY

CLASS

java.io

Object

RuntimeException

javax.swing.undo

AbstractUndoableEdit CompoundEdit UndoManager

StateEditUndoableEditSupport StateEditable

UndoableEdit

CannotRedoException

CannotUndoException

Serializable

javax.swing.event

UndoableEditListener

java.lang

Figur e 35−1: The javax.swing.undo package

AbstractUndoableEdit Ja va 1.2

javax.swing .undo serializable

This class is a simple implementation of UndoableEdit.Itenforces the restriction that an

edit cannot be undone twice or redone without first being undone. Although the undo()

and redo() methods do not actually undo or redo anything, subclasses should still call

javax.swing.

undo

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super.undo() and super.redo() in order to retain these restrictions. addEdit() and replaceEdit()

retur n false; this implementation makes no attempt to merge events. getUndoPresentation-

Name() and getRedoPresentationName() retur n the strings ...