Use Timer to control JProgressBar in Java

/*  w w w .j  a v a 2s  .c o  m*/
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JProgressBar;
import javax.swing.Timer;

public class Main {
  public static void main(String[] args) {
    final Timer  timer;
    final JProgressBar progressBar = new JProgressBar();
    final JButton button = new JButton("Start");
    JFrame f = new JFrame();
    f.setLayout(new FlowLayout());
    f.add(progressBar);
    f.add(button);

    ActionListener updateProBar = new ActionListener() {
      public void actionPerformed(ActionEvent actionEvent) {
        int val = progressBar.getValue();
        if (val >= 100) {
        //  timer.stop();
          button.setText("End");
          return;
        }
        progressBar.setValue(++val);
      }
    };
    timer = new Timer(50, updateProBar);
    button.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        if (timer.isRunning()) {
          timer.stop();
          button.setText("Start");
        } else if (button.getText() != "End") {
          timer.start();
          button.setText("Stop");
        }
      }
    });
    f.pack();
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setResizable(false);
    f.setLocationRelativeTo(null);
    f.setVisible(true);
  }
}