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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * accompanied this code).
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package javax.swing.undo;

import java.io.Serializable;
import javax.swing.UIManager;


An abstract implementation of UndoableEdit,
implementing simple responses to all boolean methods in
that interface.

Author:Ray Ryan
/**
 * An abstract implementation of <code>UndoableEdit</code>,
 * implementing simple responses to all boolean methods in
 * that interface.
 *
 * @author Ray Ryan
 */
public class AbstractUndoableEdit implements UndoableEdit, Serializable {

    
String returned by getUndoPresentationName;
as of Java 2 platform v1.3.1 this field is no longer used. This value
is now localized and comes from the defaults table with key
AbstractUndoableEdit.undoText.

See Also:
  • UIDefaults
/**
     * String returned by <code>getUndoPresentationName</code>;
     * as of Java 2 platform v1.3.1 this field is no longer used. This value
     * is now localized and comes from the defaults table with key
     * <code>AbstractUndoableEdit.undoText</code>.
     *
     * @see javax.swing.UIDefaults
     */
    protected static final String UndoName = "Undo";

    
String returned by getRedoPresentationName;
as of Java 2 platform v1.3.1 this field is no longer used. This value
is now localized and comes from the defaults table with key
AbstractUndoableEdit.redoText.

See Also:
  • UIDefaults
/**
     * String returned by <code>getRedoPresentationName</code>;
     * as of Java 2 platform v1.3.1 this field is no longer used. This value
     * is now localized and comes from the defaults table with key
     * <code>AbstractUndoableEdit.redoText</code>.
     *
     * @see javax.swing.UIDefaults
     */
    protected static final String RedoName = "Redo";

    
Defaults to true; becomes false if this edit is undone, true
again if it is redone.

/**
     * Defaults to true; becomes false if this edit is undone, true
     * again if it is redone.
     */
    boolean hasBeenDone;

    
True if this edit has not received die; defaults
to true.

/**
     * True if this edit has not received <code>die</code>; defaults
     * to <code>true</code>.
     */
    boolean alive;

    
Creates an AbstractUndoableEdit which defaults
hasBeenDone and alive to true.

/**
     * Creates an <code>AbstractUndoableEdit</code> which defaults
     * <code>hasBeenDone</code> and <code>alive</code> to <code>true</code>.
     */
    public AbstractUndoableEdit() {
        super();

        hasBeenDone = true;
        alive = true;
    }

    
Sets alive to false. Note that this
is a one way operation; dead edits cannot be resurrected.
Sending undo or redo to
a dead edit results in an exception being thrown.

Typically an edit is killed when it is consolidated by
another edit's addEdit or replaceEdit
method, or when it is dequeued from an UndoManager.

/**
     * Sets <code>alive</code> to false. Note that this
     * is a one way operation; dead edits cannot be resurrected.
     * Sending <code>undo</code> or <code>redo</code> to
     * a dead edit results in an exception being thrown.
     *
     * <p>Typically an edit is killed when it is consolidated by
     * another edit's <code>addEdit</code> or <code>replaceEdit</code>
     * method, or when it is dequeued from an <code>UndoManager</code>.
     */
    public void die() {
        alive = false;
    }

    
Throws CannotUndoException if canUndo
returns false. Sets hasBeenDone
to false. Subclasses should override to undo the
operation represented by this edit. Override should begin with
a call to super.

Throws:
  • CannotUndoException – if canUndo
   returns false
See Also:
/**
     * Throws <code>CannotUndoException</code> if <code>canUndo</code>
     * returns <code>false</code>. Sets <code>hasBeenDone</code>
     * to <code>false</code>. Subclasses should override to undo the
     * operation represented by this edit. Override should begin with
     * a call to super.
     *
     * @exception CannotUndoException if <code>canUndo</code>
     *    returns <code>false</code>
     * @see     #canUndo
     */
    public void undo() throws CannotUndoException {
        if (!canUndo()) {
            throw new CannotUndoException();
        }
        hasBeenDone = false;
    }

    
Returns true if this edit is alive
and hasBeenDone is true.

See Also:
Returns:true if this edit is alive
   and hasBeenDone is true
/**
     * Returns true if this edit is <code>alive</code>
     * and <code>hasBeenDone</code> is <code>true</code>.
     *
     * @return true if this edit is <code>alive</code>
     *    and <code>hasBeenDone</code> is <code>true</code>
     *
     * @see     #die
     * @see     #undo
     * @see     #redo
     */
    public boolean canUndo() {
        return alive && hasBeenDone;
    }

    
Throws CannotRedoException if canRedo
returns false. Sets hasBeenDone to true.
Subclasses should override to redo the operation represented by
this edit. Override should begin with a call to super.

Throws:
  • CannotRedoException – if canRedo
    returns false
See Also:
/**
     * Throws <code>CannotRedoException</code> if <code>canRedo</code>
     * returns false. Sets <code>hasBeenDone</code> to <code>true</code>.
     * Subclasses should override to redo the operation represented by
     * this edit. Override should begin with a call to super.
     *
     * @exception CannotRedoException if <code>canRedo</code>
     *     returns <code>false</code>
     * @see     #canRedo
     */
    public void redo() throws CannotRedoException {
        if (!canRedo()) {
            throw new CannotRedoException();
        }
        hasBeenDone = true;
    }

    
Returns true if this edit is alive
and hasBeenDone is false.

See Also:
Returns:true if this edit is alive
  and hasBeenDone is false
/**
     * Returns <code>true</code> if this edit is <code>alive</code>
     * and <code>hasBeenDone</code> is <code>false</code>.
     *
     * @return <code>true</code> if this edit is <code>alive</code>
     *   and <code>hasBeenDone</code> is <code>false</code>
     * @see     #die
     * @see     #undo
     * @see     #redo
     */
    public boolean canRedo() {
        return alive && !hasBeenDone;
    }

    
This default implementation returns false.

Params:
  • anEdit – the edit to be added
See Also:
Returns:false
/**
     * This default implementation returns false.
     *
     * @param anEdit the edit to be added
     * @return false
     *
     * @see UndoableEdit#addEdit
     */
    public boolean addEdit(UndoableEdit anEdit) {
        return false;
    }

    
This default implementation returns false.

Params:
  • anEdit – the edit to replace
See Also:
Returns:false
/**
     * This default implementation returns false.
     *
     * @param anEdit the edit to replace
     * @return false
     *
     * @see UndoableEdit#replaceEdit
     */
    public boolean replaceEdit(UndoableEdit anEdit) {
        return false;
    }

    
This default implementation returns true.

See Also:
Returns:true
/**
     * This default implementation returns true.
     *
     * @return true
     * @see UndoableEdit#isSignificant
     */
    public boolean isSignificant() {
        return true;
    }

    
This default implementation returns "". Used by
getUndoPresentationName and
getRedoPresentationName to
construct the strings they return. Subclasses should override to
return an appropriate description of the operation this edit
represents.

See Also:
Returns:the empty string ""
/**
     * This default implementation returns "". Used by
     * <code>getUndoPresentationName</code> and
     * <code>getRedoPresentationName</code> to
     * construct the strings they return. Subclasses should override to
     * return an appropriate description of the operation this edit
     * represents.
     *
     * @return the empty string ""
     *
     * @see     #getUndoPresentationName
     * @see     #getRedoPresentationName
     */
    public String getPresentationName() {
        return "";
    }

    
Retreives the value from the defaults table with key
AbstractUndoableEdit.undoText and returns
that value followed by a space, followed by
getPresentationName.
If getPresentationName returns "",
then the defaults value is returned alone.

See Also:
Returns:the value from the defaults table with key
   AbstractUndoableEdit.undoText, followed
   by a space, followed by getPresentationName
   unless getPresentationName is "" in which
   case, the defaults value is returned alone.
/**
     * Retreives the value from the defaults table with key
     * <code>AbstractUndoableEdit.undoText</code> and returns
     * that value followed by a space, followed by
     * <code>getPresentationName</code>.
     * If <code>getPresentationName</code> returns "",
     * then the defaults value is returned alone.
     *
     * @return the value from the defaults table with key
     *    <code>AbstractUndoableEdit.undoText</code>, followed
     *    by a space, followed by <code>getPresentationName</code>
     *    unless <code>getPresentationName</code> is "" in which
     *    case, the defaults value is returned alone.
     * @see #getPresentationName
     */
    public String getUndoPresentationName() {
        String name = getPresentationName();
        if (!"".equals(name)) {
            name = UIManager.getString("AbstractUndoableEdit.undoText") +
                " " + name;
        } else {
            name = UIManager.getString("AbstractUndoableEdit.undoText");
        }

        return name;
    }

    
Retreives the value from the defaults table with key
AbstractUndoableEdit.redoText and returns
that value followed by a space, followed by
getPresentationName.
If getPresentationName returns "",
then the defaults value is returned alone.

See Also:
Returns:the value from the defaults table with key
   AbstractUndoableEdit.redoText, followed
   by a space, followed by getPresentationName
   unless getPresentationName is "" in which
   case, the defaults value is returned alone.
/**
     * Retreives the value from the defaults table with key
     * <code>AbstractUndoableEdit.redoText</code> and returns
     * that value followed by a space, followed by
     * <code>getPresentationName</code>.
     * If <code>getPresentationName</code> returns "",
     * then the defaults value is returned alone.
     *
     * @return the value from the defaults table with key
     *    <code>AbstractUndoableEdit.redoText</code>, followed
     *    by a space, followed by <code>getPresentationName</code>
     *    unless <code>getPresentationName</code> is "" in which
     *    case, the defaults value is returned alone.
     * @see #getPresentationName
     */
    public String getRedoPresentationName() {
        String name = getPresentationName();
        if (!"".equals(name)) {
            name = UIManager.getString("AbstractUndoableEdit.redoText") +
                " " + name;
        } else {
            name = UIManager.getString("AbstractUndoableEdit.redoText");
        }

        return name;
    }

    
Returns a string that displays and identifies this
object's properties.

Returns:a String representation of this object
/**
     * Returns a string that displays and identifies this
     * object's properties.
     *
     * @return a String representation of this object
     */
    public String toString()
    {
        return super.toString()
            + " hasBeenDone: " + hasBeenDone
            + " alive: " + alive;
    }
}