hi im new to prgramming and need help with a task we're set in college, we need to make a timer i.e.
00:00:00:00
hours minutes seconds milliseconds
needs to be started witgh a start button, stopped with a stop button, reset with a reset button

any insight would be helpful and greatly appreciated, if i need to move change remove or add anything plz tell me so yh... plzzzzz help

package tasktimer;

import java.awt.Dimension;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.*;
import javax.swing.JOptionPane;
import javax.swing.JButton;
import javax.swing.JFrame;
import java.awt.event.*;
import javax.swing.JTextField;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.*;
import javax.swing.JButton;
import javax.swing.Timer;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;





public class TaskTimer extends JFrame implements ActionListener {

   private JButton start;
   private JButton stop;
   private JButton reset;
   private JPanel panel;
   private JOptionPane myOptionPane;
   private Timer myTimer;
   private JPanel drawingJPanel;
   private JLabel TimerDisplay;



   //private long startTime;
   //private long stopTime;

   public static void main(String[] args) {
   TaskTimer calculationFrame = new TaskTimer();
   calculationFrame.setSize(400,400);
   calculationFrame.createGUI();
   calculationFrame.setVisible(true);
   }

   public void createGUI() {
       setDefaultCloseOperation(EXIT_ON_CLOSE);
       Container window = this.getContentPane();
       //window.setLayout(new FlowLayout());

       panel = new JPanel();
       panel.setPreferredSize(new Dimension(700,700));
       panel.setBackground(Color.blue);
       panel.setLayout(null);
       window.add(panel);

       start = new JButton("start");
       start.setBounds(40,45,100,20);
       panel.add(start);
       start.addActionListener(this);


       stop = new JButton("stop");
       stop.setBounds(40,25,100,20);
       panel.add(stop);
       stop.addActionListener(this);

       reset = new JButton ("reset");
       reset.setBounds(40,65,100,20);
       panel.add(reset);
       reset.addActionListener(this);
       
     

       TimerDisplay = new JLabel("0");
       TimerDisplay.setBounds(200,200,500,20);
       TimerDisplay.setBackground(Color.red);
       TimerDisplay.setLayout(null);
       panel.add(TimerDisplay);
       TimerDisplay.setVisible(true);
       TimerDisplay.setForeground(Color.white);




       

   }

   public void actionPerformed(ActionEvent e) {
   if (e.getSource() == myTimer)
           if (drawingJPanel.getBackground() == Color.blue) {
               drawingJPanel.setBackground(Color.red);
           } else
               drawingJPanel.setBackground(Color.blue);

   int startingTime;
   int m = millis();
   int seconds = m / 1000;
   int minutes = seconds / 60;
   int hours = minutes / 60;
   int days = hours / 24;    
   seconds -= minutes * 60;
   minutes -= hours * 60;
   hours -= days * 24;
   String format = "This timer has been running for {0,number,integer} days {1,number,integer} hours {2,number,integer} minutes and {3,number,integer} seconds";

startingTime = millis();
   
   }

   private int millis() {
       throw new UnsupportedOperationException("Not yet implemented");
   }

   }