Java tutorial
import java.awt.BorderLayout; import java.awt.Container; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.UIDefaults; import javax.swing.UIManager; public class Main { public static void main(String args[]) { JFrame frame = new JFrame("Active Example"); UIManager.put("LabelFactory", new ActiveLabel()); final JPanel panel = new JPanel(); JButton button = new JButton("Get"); ActionListener actionListener = new ActionListener() { public void actionPerformed(ActionEvent actionEvent) { JLabel label = (JLabel) UIManager.get("LabelFactory"); panel.add(label); panel.revalidate(); } }; button.addActionListener(actionListener); Container contentPane = frame.getContentPane(); contentPane.add(panel, BorderLayout.CENTER); contentPane.add(button, BorderLayout.SOUTH); frame.setSize(200, 200); frame.setVisible(true); } } class ActiveLabel implements UIDefaults.ActiveValue { private int counter = 0; public Object createValue(UIDefaults defaults) { JLabel label = new JLabel("" + counter++); return label; } }