import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.event.UndoableEditEvent;
import javax.swing.event.UndoableEditListener;
import javax.swing.undo.UndoManager;

public class UndoWindow extends JFrame {
  private JTextArea textArea = new JTextArea();
  private UndoManager undoManager = new UndoManager();
  private JButton undo = new JButton("<");
  private JButton redo = new JButton(">");

  public UndoWindow() {
    super("Window Undo");

    JPanel button = new JPanel(new GridLayout());
    button.add(undo);
    button.add(redo);
    getContentPane().add(button, BorderLayout.SOUTH);
    getContentPane().add(new JScrollPane(textArea), BorderLayout.CENTER);

    textArea.getDocument().addUndoableEditListener(
        new UndoableEditListener() {
          public void undoableEditHappened(UndoableEditEvent e) {
            undoManager.addEdit(e.getEdit());
            update();
          }
        });

    undo.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        undoManager.undo();
        update();
      }
    });

    redo.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        undoManager.redo();
        update();
      }
    });

    setSize(450, 550);
    setVisible(true);
  }

  public void update() {
    undo.setText(undoManager.getUndoPresentationName());
    redo.setText(undoManager.getRedoPresentationName());
    undo.setEnabled(undoManager.canUndo());
    redo.setEnabled(undoManager.canRedo());
  }

  public static void main(String argv[]) {
    new UndoWindow();
  }
}