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/*******************************************************************************
 * Copyright (c) 2000, 2015 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.util;

import java.util.EventObject;
import org.eclipse.core.runtime.Assert;

/**
 * An event object describing a change to a named property.
 * 

* This concrete class was designed to be instantiated, but may * also be subclassed if required. *

*

* The JFace frameworks contain classes that report property * change events for internal state changes that may be of interest * to external parties. A special listener interface * (IPropertyChangeListener) is defined for this purpose, * and a typical class allow listeners to be registered via * an addPropertyChangeListener method. *

* * @see IPropertyChangeListener */ public class PropertyChangeEvent extends EventObject { /** * Generated serial version UID for this class. * @since 3.1 */ private static final long serialVersionUID = 3256726173533811256L; /** * The name of the changed property. */ private String propertyName; /** * The old value of the changed property, or null if * not known or not relevant. */ private Object oldValue; /** * The new value of the changed property, or null if * not known or not relevant. */ private Object newValue; /** * Creates a new property change event. * * @param source the object whose property has changed * @param property the property that has changed (must not be null) * @param oldValue the old value of the property, or null if none * @param newValue the new value of the property, or null if none */ public PropertyChangeEvent(Object source, String property, Object oldValue, Object newValue) { super(source); Assert.isNotNull(property); this.propertyName = property; this.oldValue = oldValue; this.newValue = newValue; } /** * Returns the new value of the property. * * @return the new value, or null if not known * or not relevant (for instance if the property was removed). */ public Object getNewValue() { return newValue; } /** * Returns the old value of the property. * * @return the old value, or null if not known * or not relevant (for instance if the property was just * added and there was no old value). */ public Object getOldValue() { return oldValue; } /** * Returns the name of the property that changed. *

* Warning: there is no guarantee that the property name returned * is a constant string. Callers must compare property names using * equals, not ==. *

* * @return the name of the property that changed */ public String getProperty() { return propertyName; } }




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