All Implemented Interfaces:

java.io.Serializable , java.util.EventListener , javax.swing.event.TreeModelListener
```
public class UndoHistory
 implements TreeModelListener, Serializable
                    
```
This class serves storing Test Tree state and navigating through it to give the undo/redo ability for test plan changes

Since:

2.12

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`public interface`	`UndoHistory.HistoryListener`	Interface to be implemented by components interested in UndoHistory

Field Summary

Fields
Modifier and Type	Field	Description

Constructor Summary

Constructors
Constructor	Description
`UndoHistory()`

Enum Constant Summary

Enum Constants
Enum Constant	Description

Method Summary

Modifier and Type	Method	Description
`void`	`clear()`	Clears the undo history
`void`	`add(JMeterTreeModel treeModel, String comment)`	Add tree model copy to the history This method relies on the rule that the record in history made AFTER change has been made to test plan
`void`	`undo()`
`void`	`redo()`
`boolean`	`canRedo()`
`boolean`	`canUndo()`
`void`	`treeNodesChanged(TreeModelEvent tme)`	Record the changes in the node as the undo step
`void`	`treeNodesInserted(TreeModelEvent tme)`	Record adding nodes as the undo step
`void`	`treeNodesRemoved(TreeModelEvent tme)`	Record deleting nodes as the undo step
`void`	`treeStructureChanged(TreeModelEvent tme)`	Record some other change
`static boolean`	`isEnabled()`
`void`	`registerHistoryListener(UndoHistory.HistoryListener listener)`	Register HistoryListener

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

- Constructor Detail
  - UndoHistory
```
UndoHistory()
```
- Method Detail
  - clear
```
 void clear()
```
    Clears the undo history
  - add
```
 void add(JMeterTreeModel treeModel, String comment)
```
    Add tree model copy to the history
    This method relies on the rule that the record in history made AFTER change has been made to test plan
    
    Parameters:
    
    treeModel - JMeterTreeModel
    
    comment - String
  - undo
```
 void undo()
```
  - redo
```
 void redo()
```
  - canRedo
```
 boolean canRedo()
```
    Returns:
    
    true if remaining items
  - canUndo
```
 boolean canUndo()
```
    Returns:
    
    true if not at first element
  - treeNodesChanged
```
 void treeNodesChanged(TreeModelEvent tme)
```
    Record the changes in the node as the undo step
    
    Parameters:
    
    tme - TreeModelEvent with event details
  - treeNodesInserted
```
 void treeNodesInserted(TreeModelEvent tme)
```
    Record adding nodes as the undo step
    
    Parameters:
    
    tme - TreeModelEvent with event details
  - treeNodesRemoved
```
 void treeNodesRemoved(TreeModelEvent tme)
```
    Record deleting nodes as the undo step
    
    Parameters:
    
    tme - TreeModelEvent with event details
  - treeStructureChanged
```
 void treeStructureChanged(TreeModelEvent tme)
```
    Record some other change
    
    Parameters:
    
    tme - TreeModelEvent with event details
  - isEnabled
```
 static boolean isEnabled()
```
    Returns:
    
    true if history is enabled
  - registerHistoryListener
```
 void registerHistoryListener(UndoHistory.HistoryListener listener)
```
    Register HistoryListener
    
    Parameters:
    
    listener - to add to our listeners

Class UndoHistory

Nested Class Summary

Field Summary

Constructor Summary

Enum Constant Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

UndoHistory

Method Detail

clear

add

undo

redo

canRedo

canUndo

treeNodesChanged

treeNodesInserted

treeNodesRemoved

treeStructureChanged

isEnabled

registerHistoryListener