/*
* Copyright (c) 1997, 2008, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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package javax.swing.undo;
import java.util.
Enumeration;
import java.util.
Hashtable;
import java.util.
Vector;
/**
* <P>StateEdit is a general edit for objects that change state.
* Objects being edited must conform to the StateEditable interface.</P>
*
* <P>This edit class works by asking an object to store it's state in
* Hashtables before and after editing occurs. Upon undo or redo the
* object is told to restore it's state from these Hashtables.</P>
*
* A state edit is used as follows:
* <PRE>
* // Create the edit during the "before" state of the object
* StateEdit newEdit = new StateEdit(myObject);
* // Modify the object
* myObject.someStateModifyingMethod();
* // "end" the edit when you are done modifying the object
* newEdit.end();
* </PRE>
*
* <P><EM>Note that when a StateEdit ends, it removes redundant state from
* the Hashtables - A state Hashtable is not guaranteed to contain all
* keys/values placed into it when the state is stored!</EM></P>
*
* @see StateEditable
*
* @author Ray Ryan
*/
public class
StateEdit
extends
AbstractUndoableEdit {
protected static final
String RCSID = "$Id: StateEdit.java,v 1.6 1997/10/01 20:05:51 sandipc Exp $";
//
// Attributes
//
/**
* The object being edited
*/
protected
StateEditable object;
/**
* The state information prior to the edit
*/
protected
Hashtable<
Object,
Object>
preState;
/**
* The state information after the edit
*/
protected
Hashtable<
Object,
Object>
postState;
/**
* The undo/redo presentation name
*/
protected
String undoRedoName;
//
// Constructors
//
/**
* Create and return a new StateEdit.
*
* @param anObject The object to watch for changing state
*
* @see StateEdit
*/
public
StateEdit(
StateEditable anObject) {
super();
init (
anObject,null);
}
/**
* Create and return a new StateEdit with a presentation name.
*
* @param anObject The object to watch for changing state
* @param name The presentation name to be used for this edit
*
* @see StateEdit
*/
public
StateEdit(
StateEditable anObject,
String name) {
super();
init (
anObject,
name);
}
protected void
init (
StateEditable anObject,
String name) {
this.
object =
anObject;
this.
preState = new
Hashtable<
Object,
Object>(11);
this.
object.
storeState(this.
preState);
this.
postState = null;
this.
undoRedoName =
name;
}
//
// Operation
//
/**
* Gets the post-edit state of the StateEditable object and
* ends the edit.
*/
public void
end() {
this.
postState = new
Hashtable<
Object,
Object>(11);
this.
object.
storeState(this.
postState);
this.
removeRedundantState();
}
/**
* Tells the edited object to apply the state prior to the edit
*/
public void
undo() {
super.undo();
this.
object.
restoreState(
preState);
}
/**
* Tells the edited object to apply the state after the edit
*/
public void
redo() {
super.redo();
this.
object.
restoreState(
postState);
}
/**
* Gets the presentation name for this edit
*/
public
String getPresentationName() {
return this.
undoRedoName;
}
//
// Internal support
//
/**
* Remove redundant key/values in state hashtables.
*/
protected void
removeRedundantState() {
Vector<
Object>
uselessKeys = new
Vector<
Object>();
Enumeration myKeys =
preState.
keys();
// Locate redundant state
while (
myKeys.
hasMoreElements()) {
Object myKey =
myKeys.
nextElement();
if (
postState.
containsKey(
myKey) &&
postState.
get(
myKey).
equals(
preState.
get(
myKey))) {
uselessKeys.
addElement(
myKey);
}
}
// Remove redundant state
for (int
i =
uselessKeys.
size()-1;
i >= 0;
i--) {
Object myKey =
uselessKeys.
elementAt(
i);
preState.
remove(
myKey);
postState.
remove(
myKey);
}
}
} // End of class StateEdit