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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;
}
}