Java tutorial
import java.awt.Component; import java.awt.event.ContainerAdapter; import java.awt.event.ContainerEvent; import java.awt.event.ContainerListener; import javax.swing.JFrame; public class Main { public static void main() { ContainerListener listener = new ContainerAdapter() { public void componentAdded(ContainerEvent evt) { Component c = evt.getChild(); } public void componentRemoved(ContainerEvent evt) { Component c = evt.getChild(); } }; JFrame frame = new JFrame(); frame.addContainerListener(listener); } }