PropertyChangeSupport

PropertyChangeSupport is a utility class in the Java Platform that implements the listener pattern for bound properties. Located in the java.beans package, it provides a convenient way for JavaBeans components to manage PropertyChangeListener objects and to publish PropertyChangeEvents when a bound property changes.

A bean can create a PropertyChangeSupport instance, typically initialized with the bean as the source. It exposes methods to add and remove listeners, either globally or for a specific property, and to query current listeners. The primary mechanism for notifying listeners is by calling firePropertyChange with the property name and either the old and new values, or a PropertyChangeEvent. Overloaded firePropertyChange methods exist for Object values as well as primitive types such as boolean, int, long, float, and double.

When a property value is updated, the bean checks for a real change and then invokes the appropriate firePropertyChange variant. Listeners registered for the specific property receive the event; those registered without a property name receive all events. The class is designed to be thread-safe for listener management and makes a snapshot of listeners to minimize synchronization during dispatch.

PropertyChangeSupport is commonly used to implement bound properties in JavaBeans and to decouple property change notification from property logic. It is often used in GUI applications and other event-driven components. See also: PropertyChangeListener, PropertyChangeEvent, java.beans package.