title: How to refresh the JComboBox data?
body: <p>I am having trouble refreshing the data inside the <code>JComboBox</code>.</p>
  
  <p>There is a button "<code>Create</code>" which has <code>ActionListener</code>, which adds the item to <code>JComboBox</code>.</p>
  
  <p>But the changes are not reflected in the GUI: I still don't see the new added item.</p>
  
  <p><code>repaint()</code> doesn't help.</p>
  
  <p>Update: Here is a (almost) full GUI code:</p>
  
  <pre><code>public class Main extends JFrame implements ActionListener
  {
      static Connection conn;
      static PreparedStatement ps = null;
      static ResultSet res;
  
      static Statement sta;
  
  private final static int ITERATION_NUMBER = 1000;
  
  public void GUI () throws SQLException {
      setBounds(0, 0, 320, 240);
      addWindowListener(new WindowAdapter(){
      public void windowClosing(WindowEvent we){
          close(ps);
          close(res);
          close(conn);
          System.exit(0);
          }
      });
      setMinimumSize(new Dimension(320, 240));
      setResizable(false);
  
      this.setTitle("Accounts");
  
      JPanel panel = new JPanel();
      GridLayout2 GL = new GridLayout2(4,3);
      GL.setHgap(10);
      panel.setLayout(GL);
  
      Font font = new Font("Serif", Font.BOLD, 20);
      Font font2 = new Font("Courier New", Font.BOLD, 16);
  
      JLabel label1 = new JLabel("Username");
      JLabel label2 = new JLabel("Password");
      JLabel label3 = new JLabel("Controls");
  
      label1.setFont(font2);
      label2.setFont(font2);
      label3.setFont(font2);
  
      final JTextField username = new JTextField();
      final JTextField password1 = new JPasswordField();
      final JTextField password2 = new JPasswordField();
  
      final JComboBox userBox1 = new JComboBox();
      final JComboBox userBox2 = new JComboBox();
  
      JButton create = new JButton("CREATE");
  
      create.addActionListener(new ActionListener() {
          public void actionPerformed(ActionEvent e)
          {
              try {
                  createUser(conn, username.getText(), password1.getText());
  userBox1.addItem(username.getText());
                  userBox2.addItem(username.getText());
              } catch (NoSuchAlgorithmException
                      | UnsupportedEncodingException | SQLException e1) {
                  // TODO Auto-generated catch block
                  e1.printStackTrace();
              }
          }
      });
  
  
  
      userBox1.removeAllItems();
      userBox2.removeAllItems();
  
      res = (ResultSet) sta.executeQuery("SELECT LOGIN FROM ACCOUNTS");
  
      String temp;
  
      for (int i=0; res.next(); i++) {
          temp = (String)res.getString("LOGIN");
          userBox1.addItem(temp);
          userBox2.addItem(temp);
      }
  
      panel.add(label1);
      panel.add(label2);
      panel.add(label3);
  
      panel.add(username);
      panel.add(password1);
      panel.add(create);
  
      panel.add(userBox1);
      panel.add(password2);
      panel.add(modify);
  
      panel.add(userBox2);
      panel.add(new JLabel(""));
      panel.add(delete);
  
      add(panel);
  
      setVisible(true);
  }
  </code></pre>
  
  <p><strong>SOLUTION:</strong> Adding password1.setText(""); just after "createUser" solved the problem! That's strange, maybe it somehow refreshed the GUI...</p>