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import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Container;
import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JToolBar;
import javax.swing.UIManager;
import javax.swing.undo.CannotUndoException;
import javax.swing.undo.UndoManager;
public class MainClass {
public static void main(final String args[]) {
JFrame frame = new JFrame("Undo Sample");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JTextArea textArea = new JTextArea();
JScrollPane scrollPane = new JScrollPane(textArea);
UndoManager manager = new UndoManager();
textArea.getDocument().addUndoableEditListener(manager);
JToolBar toolbar = new JToolBar();
JButton undoButton = new JButton(new UndoAction(manager, (String) UIManager
.get("AbstractUndoableEdit.undoText")));
toolbar.add(undoButton);
Container content = frame.getContentPane();
content.add(toolbar, BorderLayout.NORTH);
content.add(scrollPane, BorderLayout.CENTER);
frame.setSize(300, 150);
frame.setVisible(true);
}
}
abstract class UndoRedoAction extends AbstractAction {
UndoManager undoManager = new UndoManager();
String errorMessage = "Cannot undo";
String errorTitle = "Undo Problem";
protected UndoRedoAction(UndoManager manager, String name) {
super(name);
undoManager = manager;
}
public void setErrorMessage(String newValue) {
errorMessage = newValue;
}
public void setErrorTitle(String newValue) {
errorTitle = newValue;
}
protected void showMessage(Object source) {
if (source instanceof Component) {
JOptionPane.showMessageDialog((Component) source, errorMessage, errorTitle,
JOptionPane.WARNING_MESSAGE);
} else {
System.err.println(errorMessage);
}
}
}
class UndoAction extends UndoRedoAction {
public UndoAction(UndoManager manager, String name) {
super(manager, name);
setErrorMessage("Cannot undo");
setErrorTitle("Undo Problem");
}
public void actionPerformed(ActionEvent actionEvent) {
try {
undoManager.undo();
} catch (CannotUndoException cannotUndoException) {
showMessage(actionEvent.getSource());
}
}
}
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