javautilEventListener

The `java.util.EventListener` interface is a marker interface defined in the Java Platform, Standard Edition. It has no methods of its own and exists solely to provide a common superclass for all event listener types. Implementors of this interface are typically used to receive notifications related to events that are generated by components, such as user interface widgets, container events, or property change events.

Because it is a marker interface, classes that implement `java.util.EventListener` can be identified via the `instanceof` operator or by checking for the interface in reflection. This enables generic event handling code to accept any listener type while ensuring that only valid listener objects are attached to event sources.

In practice, many of Java’s event-driven APIs extend from this base interface. For example, `java.awt.event.ActionListener` is used to handle button clicks, `java.beans.PropertyChangeListener` listens for bean property changes, and `java.util.EventListener` is also the superinterface for listeners used in the JavaBeans event model. These subinterfaces add the specific method(s) required to handle a particular event type.

Typical usage involves registering a listener on a source object and then overriding the callback method that the listener interface specifies. A minimal example would be:

```

class MyAction implements java.awt.event.ActionListener {

public void actionPerformed(java.awt.event.ActionEvent e) {

System.out.println("Button pressed");

}

}

JButton button = new JButton("Click");

button.addActionListener(new MyAction());

```

The `java.util.EventListener` interface serves as the foundation for Java’s flexible and extensible event handling system, allowing event producers and consumers to remain loosely coupled.