Java JFrame create date formatter viewer

import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.SimpleDateFormat;
import java.util.Date;

import javax.swing.BorderFactory;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JComboBox;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class Main extends JPanel implements ActionListener {
  static JFrame frame;
  JLabel result;// w  w w. jav  a  2  s.  c o m
  String currentPattern;

  public Main() {
    setLayout(new BoxLayout(this, BoxLayout.PAGE_AXIS));
    String[] patternExamples = { "dd MMMMM yyyy", "dd.MM.yy", "MM/dd/yy",
        "yyyy.MM.dd G 'at' hh:mm:ss z", "EEE, MMM d, ''yy", "h:mm a",
        "H:mm:ss:SSS", "K:mm a,z", "yyyy.MMMMM.dd GGG hh:mm aaa" };

    currentPattern = patternExamples[0];

    JLabel patternLabel1 = new JLabel("Enter pattern or select list:");

    JComboBox<String> patternList = new JComboBox<>(patternExamples);
    patternList.setEditable(true);
    patternList.addActionListener(this);

    JLabel resultLabel = new JLabel("Current Date/Time", JLabel.LEADING); // LEFT
    result = new JLabel(" ");
    result.setForeground(Color.black);
    result.setBorder(BorderFactory.createCompoundBorder(BorderFactory
        .createLineBorder(Color.black), BorderFactory.createEmptyBorder(5, 5,
        5, 5)));

    JPanel patternPanel = new JPanel();
    patternPanel.setLayout(new BoxLayout(patternPanel, BoxLayout.PAGE_AXIS));
    patternPanel.add(patternLabel1);
    patternList.setAlignmentX(Component.LEFT_ALIGNMENT);
    patternPanel.add(patternList);

    JPanel resultPanel = new JPanel(new GridLayout(0, 1));
    resultPanel.add(resultLabel);
    resultPanel.add(result);

    patternPanel.setAlignmentX(Component.LEFT_ALIGNMENT);
    resultPanel.setAlignmentX(Component.LEFT_ALIGNMENT);

    add(patternPanel);
    add(Box.createRigidArea(new Dimension(0, 10)));
    add(resultPanel);

    setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));

    reformat();
  }

  public void actionPerformed(ActionEvent e) {
    JComboBox cb = (JComboBox) e.getSource();
    String newSelection = (String) cb.getSelectedItem();
    currentPattern = newSelection;
    reformat();
  }
  public void reformat() {
    Date today = new Date();
    SimpleDateFormat formatter = new SimpleDateFormat(currentPattern);
    try {
      String dateString = formatter.format(today);
      result.setForeground(Color.black);
      result.setText(dateString);
    } catch (IllegalArgumentException iae) {
      result.setForeground(Color.red);
      result.setText("Error: " + iae.getMessage());
    }
  }
  public static void main(String[] args) {
     JFrame frame = new JFrame("Testing Date Formatter");
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     JComponent newContentPane = new Main();
     frame.setContentPane(newContentPane);
     frame.pack();
     frame.setVisible(true);
  }
}