I noted this (it's a java.awt.event class).

public abstract class MouseAdapter implements MouseListener, 
                                              MouseWheelListener, 
                                              MouseMotionListener {
....
}

Then you are clearly forced to extend from this adapter

public class MouseAdapterImpl extends MouseAdapter {}

the class is abstract and implements no methods. Is this a strategy to combine different interfaces into a single "basically interface" ? I assume in java it's not possible to combine different interfaces into a single one without using this approach.

In other words, it's not possible to do something like this in java

public interface MouseAdapterIface extends MouseListener, 
                                           MouseWheelListener, 
                                           MouseMotionListener {
}

and then eventually

public class MouseAdapterImpl implements MouseAdapterIface {}

Is my understanding of the point correct ? what about C# ?