title: Changing the content of jTextField while typing
body: <p>I'm trying to reset my JTextField in case that Space is typed. It throws me:</p>
  
  <p><code>Exception in thread "AWT-EventQueue-0" java.lang.IllegalStateException: Attempt to mutate in notification</code></p>
  
  <p>my code is:</p>
  
  <pre><code>import java.awt.Color;
  import java.awt.EventQueue;
  import javax.swing.JDesktopPane;
  import javax.swing.JFrame;
  import javax.swing.JPanel;
  import javax.swing.JTextField;
  import javax.swing.border.EmptyBorder;
  import javax.swing.event.DocumentEvent;
  import javax.swing.event.DocumentListener;
  
  public class MainFrame extends JFrame {
  
      private JPanel contentPane;
      private JTextField textField;
  
      /** * Launch the application. */
      public static void main(String[] args) {
          EventQueue.invokeLater(new Runnable() {
              public void run() {
                  try {
                      MainFrame frame = new MainFrame();
                      frame.setVisible(true);
                  } catch (Exception e) {
                      e.printStackTrace();
                  }
              }
          });
      }
  
      /** * Create the frame. */
      public MainFrame() {
          setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          setBounds(100, 100, 450, 300);
          contentPane = new JPanel();
          contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
          setContentPane(contentPane);
          contentPane.setLayout(null);
  
          JDesktopPane desktopPane = new JDesktopPane();
          desktopPane.setBackground(Color.LIGHT_GRAY);
          desktopPane.setBounds(6, 6, 438, 266);
          contentPane.add(desktopPane);
  
          textField = new JTextField();
          textField.getDocument().addDocumentListener(new DocumentListener() {
              public void changedUpdate(DocumentEvent e) {
              }
  
              public void removeUpdate(DocumentEvent e) {
              }
  
              public void insertUpdate(DocumentEvent e) {
                  if (textField.getText().contains(" ")) {
                      System.out
                              .println("Space was entered! clearing the  text field");
                      textField.setText("");
                  }
              }
          });
          textField.setBounds(133, 112, 134, 28);
          desktopPane.add(textField);
          textField.setColumns(10);
      }
  }
  </code></pre>