```
public class mxUndoManager
extends mxEventSource
```
Implements an undo history. This class fires the following events: mxEvent.CLEAR fires after clear was executed. The event has no properties. mxEvent.UNDO fires afer a significant edit was undone in undo. The edit property contains the mxUndoableEdit that was undone. mxEvent.REDO fires afer a significant edit was redone in redo. The edit property contains the mxUndoableEdit that was redone. mxEvent.ADD fires after an undoable edit was added to the history. The edit property contains the mxUndoableEdit that was added.

Nested Class Summary
- Nested classes/interfaces inherited from class com.mxgraph.util.mxEventSource
  mxEventSource.mxIEventListener

Fields
Modifier and Type	Field	Description
`protected java.util.List<mxUndoableEdit>`	`history`	List that contains the steps of the command history.
`protected int`	`indexOfNextAdd`	Index of the element to be added next.
`protected int`	`size`	Maximum command history size.

Fields inherited from class com.mxgraph.util.mxEventSource
eventListeners, eventsEnabled, eventSource

Constructors
Constructor	Description
`mxUndoManager()`	Constructs a new undo manager with a default history size.
`mxUndoManager(int size)`	Constructs a new undo manager for the specified size.

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`boolean`	`canRedo()`	Returns true if a redo is possible.
`boolean`	`canUndo()`	Returns true if an undo is possible.
`void`	`clear()`	Clears the command history.
`boolean`	`isEmpty()`
`void`	`redo()`	Redoes the last change.
`protected void`	`trim()`	Removes all pending steps after indexOfNextAdd from the history, invoking die on each edit.
`void`	`undo()`	Undoes the last change.
`void`	`undoableEditHappened(mxUndoableEdit undoableEdit)`	Method to be called to add new undoable edits to the history.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Class mxUndoManager