Property change event concept

UML model uses standard java.beans.PropertyChangeEvent events for notifying listeners about changes.  

The main properties of the PropertyChangeEvent are as follows:

• Property name. The changed property name.
• New value. The new (current) changed property value.
• Old value. The old property value, which was before the property change.

    propertyChangeEvent.getPropertyName().equals(PropertyNames.NAME); 
    propertyChangeEvent.getNewValue() // will be new name of element; 
    propertyChangeEvent.getOldValue() // will be name of element before change.

Example of the new element creation event

    propertyChangeEvent.getPropertyName().equals(UML2MetamodelConstants.INSTANCE_CREATED); 
    propertyChangeEvent.getNewValue() // will be new created element; 
    propertyChangeEvent.getOldValue() // will be null.