All Implemented Interfaces:

CleanUpHandler
```
public class Undo
extends Object
implements CleanUpHandler
```
A general Undo/Redo-mechanism: stores objects either in memory or on disk. The objects have to be serializable.

Author:

fracpete (fracpete at waikato dot ac dot nz)

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static class Undo.UndoPoint
Represents a single undo point, i.e., data and comment.

Field Summary

Fields
Modifier and Type	Field	Description
`static int`	`COMMENT_MAX_LENGTH`	the maximum length for a comment.
`static int`	`DEFAULT_MAX_UNDO`	the default for number of undo steps.
`protected boolean`	`m_Enabled`	whether undo is currently enabled or not.
`protected HashSet<UndoListener>`	`m_Listeners`	the list of listeners.
`protected int`	`m_MaxCommentLength`	the maximum length for comments before shortening.
`protected int`	`m_MaxUndo`	the maximum number of undo points.
`protected boolean`	`m_OnDisk`	whether to store the objects on disk.
`protected List<Undo.UndoPoint>`	`m_RedoList`	the vector for the redo-points objects.
`protected ShorteningType`	`m_ShorteningType`	where to shorten the comments.
`protected Class`	`m_UndoClass`	the class for which the undo is.
`protected List<Undo.UndoPoint>`	`m_UndoList`	the vector for the undo-points objects.
`protected boolean`	`m_Working`	whether the object is currently working, e.g., performing an undo/redo.

Constructor Summary

Constructors
Constructor	Description
`Undo()`	Initializes the undo mechanism.
`Undo(Class undoClass)`	Initializes the undo mechanism for the specified class (in memory).
`Undo(Class undoClass, boolean onDisk)`	Initializes the undo mechanism for the specified class.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`boolean`	`addRedo(Object o, String comment)`	Adds the object to the redo list.
`boolean`	`addUndo(Object o, String comment)`	Adds the object to the undo list, throws the Redo list away.
`boolean`	`addUndo(Object o, String comment, boolean keepRedo)`	Adds the object to the undo list.
`void`	`addUndoListener(UndoListener l)`	Adds the listener to the internal list.
`boolean`	`canRedo()`	Returns whether any redo-steps are left.
`boolean`	`canUndo()`	Returns whether any undo-steps are left.
`void`	`cleanUp()`	Cleans up data structures, frees up memory.
`protected void`	`cleanUp(List<Undo.UndoPoint> list)`	If "onDisk" is active, removes all files from disk, otherwise it only empties the list.
`void`	`clear()`	Clears the undo and redo list.
`int`	`getMaxCommentLength()`	Returns the maximum length for comments before shortening them.
`int`	`getMaxUndo()`	Returns the maximum number of undo steps to allow.
`boolean`	`getOnDisk()`	Returns whether the objects are stored on disk (only possible for serializable ones) or held in memory.
`ShorteningType`	`getShorteningType()`	Returns how to shorten the comments.
`Class`	`getUndoClass()`	Returns the class this undo mechanism is for.
`boolean`	`isEnabled()`	Returns whether undo is currently enabled or not.
`boolean`	`isWorking()`	Returns whether undo/redo is currently performed.
`protected void`	`notifyListeners(UndoEvent e)`	notifies all listeners with the specified event.
`Undo.UndoPoint`	`peekRedo()`	"Peeks" at the last redo item.
`String`	`peekRedoComment()`	Returns the comment of the last redo point.
`Undo.UndoPoint`	`peekUndo()`	"Peeks" at the last undo item.
`String`	`peekUndoComment()`	Returns the comment of the last undo point.
`Undo.UndoPoint`	`redo()`	Returns the object from the next redo step and removes it from its internal list.
`protected Undo.UndoPoint`	`redo(boolean notify)`	Returns the object from the next redo step and removes it from its internal list.
`void`	`removeUndoListener(UndoListener l)`	Removes the listener from the internal list.
`void`	`setEnabled(boolean value)`	Sets the enabled state, i.e., either enables or disables the undo.
`void`	`setMaxCommentLength(int value)`	Sets the maximum length for comments before shortening them.
`void`	`setMaxUndo(int value)`	Sets the maximum number of undo steps to allow.
`void`	`setShorteningType(ShorteningType value)`	Sets how to shorten the comments.
`protected String`	`shortenComment(String s)`	Shortens the comment.
`Undo.UndoPoint`	`undo()`	Returns the object from the next undo step and removes it from its internal list.
`protected Undo.UndoPoint`	`undo(boolean notify)`	Returns the object from the next undo step and removes it from its internal list.

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

- Field Detail
  - COMMENT_MAX_LENGTH
```
public static final int COMMENT_MAX_LENGTH
```
    the maximum length for a comment.
    
    See Also:
    
    Constant Field Values
  - DEFAULT_MAX_UNDO
```
public static final int DEFAULT_MAX_UNDO
```
    the default for number of undo steps.
    
    See Also:
    
    Constant Field Values
  - m_UndoClass
```
protected Class m_UndoClass
```
    the class for which the undo is.
  - m_OnDisk
```
protected boolean m_OnDisk
```
    whether to store the objects on disk.
  - m_UndoList
```
protected List<Undo.UndoPoint> m_UndoList
```
    the vector for the undo-points objects.
  - m_RedoList
```
protected List<Undo.UndoPoint> m_RedoList
```
    the vector for the redo-points objects.
  - m_Listeners
```
protected HashSet<UndoListener> m_Listeners
```
    the list of listeners.
  - m_Enabled
```
protected boolean m_Enabled
```
    whether undo is currently enabled or not.
  - m_Working
```
protected boolean m_Working
```
    whether the object is currently working, e.g., performing an undo/redo.
  - m_MaxUndo
```
protected int m_MaxUndo
```
    the maximum number of undo points.
  - m_ShorteningType
```
protected ShorteningType m_ShorteningType
```
    where to shorten the comments.
  - m_MaxCommentLength
```
protected int m_MaxCommentLength
```
    the maximum length for comments before shortening.
- Constructor Detail
  - Undo
```
public Undo()
```
    Initializes the undo mechanism. Maximum of DEFAULT_MAX_UNDO undo steps.
    
    See Also:
    
    setMaxUndo(int), DEFAULT_MAX_UNDO
  - Undo
```
public Undo(Class undoClass)
```
    Initializes the undo mechanism for the specified class (in memory). Maximum of DEFAULT_MAX_UNDO undo steps.
    
    Parameters:
    
    undoClass - the class for which the undo is setup
    
    See Also:
    
    setMaxUndo(int), DEFAULT_MAX_UNDO
  - Undo
```
public Undo(Class undoClass,
            boolean onDisk)
```
    Initializes the undo mechanism for the specified class. Maximum of DEFAULT_MAX_UNDO undo steps.
    
    Parameters:
    
    undoClass - the class for which the undo is setup
    
    onDisk - whether to store the objects on disk (when they're serializable)
    
    See Also:
    
    setMaxUndo(int), DEFAULT_MAX_UNDO
- Method Detail
  - getUndoClass
```
public Class getUndoClass()
```
    Returns the class this undo mechanism is for.
    
    Returns:
    
    the class this undo is for
  - getOnDisk
```
public boolean getOnDisk()
```
    Returns whether the objects are stored on disk (only possible for serializable ones) or held in memory.
    
    Returns:
    
    true if the objects are stored on disk
  - isEnabled
```
public boolean isEnabled()
```
    Returns whether undo is currently enabled or not.
    
    Returns:
    
    true if undo is enabled
  - setEnabled
```
public void setEnabled(boolean value)
```
    Sets the enabled state, i.e., either enables or disables the undo.
    
    Parameters:
    
    value - if true then the undo will be enabled.
  - setMaxUndo
```
public void setMaxUndo(int value)
```
    Sets the maximum number of undo steps to allow. Can only be set before the first undo/redo happens.
    
    Parameters:
    
    value - the number of undo steps, use -1 for unlimited
  - getMaxUndo
```
public int getMaxUndo()
```
    Returns the maximum number of undo steps to allow.
    
    Returns:
    
    the number of undo steps, -1 if unlimited
  - isWorking
```
public boolean isWorking()
```
    Returns whether undo/redo is currently performed.
    
    Returns:
    
    true if an undo/redo is currently performed
  - addUndo
```
public boolean addUndo(Object o,
                       String comment)
```
    Adds the object to the undo list, throws the Redo list away.
    
    Parameters:
    
    o - the object to add to the undo list
    
    comment - the comment to associate with the undo point
    
    Returns:
    
    true if the object was added successfully
  - addUndo
```
public boolean addUndo(Object o,
                       String comment,
                       boolean keepRedo)
```
    Adds the object to the undo list.
    
    Parameters:
    
    o - the object to add to the undo list
    
    comment - the comment to associate with the undo point
    
    keepRedo - whether to keep the redo list
    
    Returns:
    
    true if the object was added successfully
  - addRedo
```
public boolean addRedo(Object o,
                       String comment)
```
    Adds the object to the redo list.
    
    Parameters:
    
    o - the object to add to the redo list
    
    comment - the comment to associate with the redo point
    
    Returns:
    
    true if the object was added successfully
  - canUndo
```
public boolean canUndo()
```
    Returns whether any undo-steps are left.
    
    Returns:
    
    true if at least one undo-step is left
  - undo
```
public Undo.UndoPoint undo()
```
    Returns the object from the next undo step and removes it from its internal list.
    
    Returns:
    
    the next undo object
  - peekUndo
```
public Undo.UndoPoint peekUndo()
```
    "Peeks" at the last undo item.
    
    Returns:
    
    the last undo item
  - peekUndoComment
```
public String peekUndoComment()
```
    Returns the comment of the last undo point.
    
    Returns:
    
    the comment
  - undo
```
protected Undo.UndoPoint undo(boolean notify)
```
    Returns the object from the next undo step and removes it from its internal list.
    
    Parameters:
    
    notify - whether a notify event should be sent
    
    Returns:
    
    the next undo object, or null if not successful
  - canRedo
```
public boolean canRedo()
```
    Returns whether any redo-steps are left.
    
    Returns:
    
    true if at least one redo-step is left
  - redo
```
public Undo.UndoPoint redo()
```
    Returns the object from the next redo step and removes it from its internal list.
    
    Returns:
    
    the next undo object
  - peekRedo
```
public Undo.UndoPoint peekRedo()
```
    "Peeks" at the last redo item.
    
    Returns:
    
    the last redo item
  - peekRedoComment
```
public String peekRedoComment()
```
    Returns the comment of the last redo point.
    
    Returns:
    
    the comment
  - redo
```
protected Undo.UndoPoint redo(boolean notify)
```
    Returns the object from the next redo step and removes it from its internal list.
    
    Parameters:
    
    notify - whether a notify event should be sent
    
    Returns:
    
    the next redo object, or null if not successful
  - cleanUp
```
protected void cleanUp(List<Undo.UndoPoint> list)
```
    If "onDisk" is active, removes all files from disk, otherwise it only empties the list.
    
    Parameters:
    
    list - the undo points to clean up
  - clear
```
public void clear()
```
    Clears the undo and redo list.
  - addUndoListener
```
public void addUndoListener(UndoListener l)
```
    Adds the listener to the internal list.
    
    Parameters:
    
    l - the listener to add
  - removeUndoListener
```
public void removeUndoListener(UndoListener l)
```
    Removes the listener from the internal list.
    
    Parameters:
    
    l - the listener to remove
  - notifyListeners
```
protected void notifyListeners(UndoEvent e)
```
    notifies all listeners with the specified event.
    
    Parameters:
    
    e - the event to send
  - setShorteningType
```
public void setShorteningType(ShorteningType value)
```
    Sets how to shorten the comments.
    
    Parameters:
    
    value - the type
  - getShorteningType
```
public ShorteningType getShorteningType()
```
    Returns how to shorten the comments.
    
    Returns:
    
    the type
  - setMaxCommentLength
```
public void setMaxCommentLength(int value)
```
    Sets the maximum length for comments before shortening them.
    
    Parameters:
    
    value - the maximum length
  - getMaxCommentLength
```
public int getMaxCommentLength()
```
    Returns the maximum length for comments before shortening them.
    
    Returns:
    
    the maximum length
  - shortenComment
```
protected String shortenComment(String s)
```
    Shortens the comment.
    
    Parameters:
    
    s - the comment to process
    
    Returns:
    
    the (potentially) shortened comment
  - cleanUp
```
public void cleanUp()
```
    Cleans up data structures, frees up memory.
    
    Specified by:
    
    cleanUp in interface CleanUpHandler

Class Undo

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

COMMENT_MAX_LENGTH

DEFAULT_MAX_UNDO

m_UndoClass

m_OnDisk

m_UndoList

m_RedoList

m_Listeners

m_Enabled

m_Working

m_MaxUndo

m_ShorteningType

m_MaxCommentLength

Constructor Detail

Undo

Undo

Undo

Method Detail

getUndoClass

getOnDisk

isEnabled

setEnabled

setMaxUndo

getMaxUndo

isWorking

addUndo

addUndo

addRedo

canUndo

undo

peekUndo

peekUndoComment

undo

canRedo

redo

peekRedo

peekRedoComment

redo

cleanUp

clear

addUndoListener

removeUndoListener

notifyListeners

setShorteningType

getShorteningType

setMaxCommentLength

getMaxCommentLength

shortenComment

cleanUp