import java.awt.event.MouseAdapter; import java.awt.event.MouseEvent; public class MouseListenerExample extends MouseAdapter { public void mouseClicked(MouseEvent e) { if (e.isAltDown()) { // do something if Alt key was pressed during the mouse click } } }In this example, we have defined a MouseListener which checks whether the Alt key was pressed during the mouse click event using the isAltDown() method of the MouseEvent class. The package library for this class is java.awt.event which is part of the Java AWT (Abstract Window Toolkit) package.