Java by API/java.awt.event/ComponentListener

implements ComponentListener

 
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ruponentEvent;
import java.awt.event.ruponentListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JSplitPane;
public class Main {
  public static void main(String args[]) {
    JFrame frame = new JFrame();
    Container contentPane = frame.getContentPane();
    ComponentListener comp = new ComponentListener() {
      public void componentHidden(ComponentEvent e) {
        dump("Hidden", e);
      }
      public void componentMoved(ComponentEvent e) {
        dump("Moved", e);
      }
      public void componentResized(ComponentEvent e) {
        dump("Resized", e);
      }
      public void componentShown(ComponentEvent e) {
        dump("Shown", e);
      }
      private void dump(String type, ComponentEvent e) {
        System.out.println(e.getComponent().getName() + " : " + type);
      }
    };
    JButton left = new JButton("Left");
    left.setName("Left");
    left.addComponentListener(comp);
    final JButton right = new JButton("Right");
    right.setName("Right");
    right.addComponentListener(comp);
    ActionListener action = new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        right.setVisible(!right.isVisible());
      }
    };
    left.addActionListener(action);
    JSplitPane pane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, true,
        left, right);
    contentPane.add(pane, BorderLayout.CENTER);
    frame.setSize(300, 200);
    frame.show();
  }
}