/*
* Copyright (c) 1997, 2008, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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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