001/*
002 * ============================================================================
003 *  Copyright © 2002-2024 by Thomas Thrien.
004 *  All Rights Reserved.
005 * ============================================================================
006 *  Licensed to the public under the agreements of the GNU Lesser General Public
007 *  License, version 3.0 (the "License"). You may obtain a copy of the License at
008 *
009 *       http://www.gnu.org/licenses/lgpl.html
010 *
011 *  Unless required by applicable law or agreed to in writing, software
012 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
013 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
014 *  License for the specific language governing permissions and limitations
015 *  under the License.
016 */
017
018package org.tquadrat.foundation.fx.beans;
019
020import static org.apiguardian.api.API.Status.STABLE;
021
022import org.apiguardian.api.API;
023import org.tquadrat.foundation.annotation.ClassVersion;
024import javafx.beans.InvalidationListener;
025import javafx.beans.Observable;
026
027/**
028 *  <p>{@summary An implementation of the
029 *  {@link Observable}
030 *  interface that just serves as a placeholder.}</p>
031 *  <p>As an instance of this class will never change its state, it will never
032 *  call any of the registered listeners; consequently, a listener added by a
033 *  call to
034 *  {@link #addListener(InvalidationListener)}
035 *  will not even be stored somewhere, so that a call to
036 *  {@link #removeListener(InvalidationListener)}
037 *  won't do anything either.</p>
038 *  <p>It is useful when creating bindings that do not change their status.</p>
039 *
040 *  @extauthor Thomas Thrien - thomas.thrien@tquadrat.org
041 *  @version $Id: ObservablePlaceholder.java 1110 2024-03-04 15:26:06Z tquadrat $
042 *  @since 0.4.2
043 *
044 *  @UMLGraph.link
045 */
046@ClassVersion( sourceVersion = "$Id: ObservablePlaceholder.java 1110 2024-03-04 15:26:06Z tquadrat $" )
047@API( status = STABLE, since = "0.4.2" )
048public final class ObservablePlaceholder implements Observable
049{
050        /*--------------*\
051    ====** Constructors **=====================================================
052        \*--------------*/
053    /**
054     *  Creates a new instance of {@code ObservablePlaceholder}.
055     */
056    public ObservablePlaceholder() { /* Just exists */ }
057
058        /*---------*\
059    ====** Methods **==========================================================
060        \*---------*/
061    /**
062     *  {@inheritDoc}
063     */
064    @Override
065    public final void addListener( final InvalidationListener listener ) { /* Does nothing */ }
066
067    /**
068     *  {@inheritDoc}
069     */
070    @Override
071    public final void removeListener( final InvalidationListener listener ) { /* Does nothing */ }
072}
073//  class ObservablePlaceholder
074
075/*
076 *  End of File
077 */