stopwatch.java

// Java program to illustrate
// digital stop watch
// using Applets

// importing required packages
import java.applet.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class GeeksforGeeks extends Applet implements Runnable, ActionListener {
	
// Panel to keep all the buttons and labels
	Panel p;
	Label display;

	// Button
	Button start, stop, reset;

	// Time
	int hour, minute, second, millisecond;

	// string to be displayed on the label
	String disp;

	// State of stopwatch on/off
	boolean on;

	// initialization
	public void init()
	{
		// initially off
		on = false;

		p = new Panel();
		// Setting layout of the panel
		p.setLayout(new GridLayout(4, 1, 6, 10));

		// initial time 00 : 00 : 00 : 000
		hour = minute = second = millisecond = 0;

		// Label
		display = new Label();
		disp = "00 : 00 : 00 : 000";
		display.setText(disp);
		p.add(display);

		// Start button
		start = new Button("Start");
		start.addActionListener((ActionListener) this);
		p.add(start);

		// Reset button
		reset = new Button("Reset");
		reset.addActionListener((ActionListener) this);
		p.add(reset);

		// Stop button
		stop = new Button("Stop");
		stop.addActionListener((ActionListener) this);
		p.add(stop);

		add(p);

		// starting thread
		new Thread(this, "StopWatch").start();
	}

	// Reset Function
	// reset to default value
	public void reset()
	{
		try {
			Thread.sleep(1);
		}
		catch (Exception e) {
			System.out.println(e);
		}
		hour = minute = second = millisecond = 0;
	}

	// update function
	// update the timer
	public void update()
	{
		millisecond++;
		if (millisecond == 1000) {
			millisecond = 0;
			second++;
			if (second == 60) {
				second = 0;
				minute++;
				if (minute == 60) {
					minute = 0;
					hour++;
				}
			}
		}
	}

	// changing label
	public void changeLabel()
	{

		// Properly formatting the display of the timer
		if (hour < 10)
			disp = "0" + hour + " : ";
		else
			disp = hour + " : ";

		if (minute < 10)
			disp += "0" + minute + " : ";
		else
			disp += minute + " : ";

		if (second < 10)
			disp += "0" + second + " : ";
		else
			disp += second + " : ";

		if (millisecond < 10)
			disp += "00" + millisecond;
		else if (millisecond < 100)
			disp += "0" + millisecond;
		else
			disp += millisecond;

		display.setText(disp);
	}

	// thread.run function
	public void run()
	{

		// while the stopwatch is on
		while (on) {
			try {
				// pause 1 millisecond
				Thread.sleep(1);
				// update the time
				update();
				// changeLabel
				changeLabel();
			}
			catch (InterruptedException e) {
				System.out.println(e);
			}
		}
	}

	// actionPerformed
	// To listen to the actions on the buttons
	public void actionPerformed(ActionEvent e)
	{

		// start a thread when start button is clicked
		if (e.getSource() == start) {
			// stopwatch is on
			on = true;
			new Thread(this, "StopWatch").start();
		}

		// reset
		if (e.getSource() == reset) {
			// stopwatch off
			on = false;
			reset();
			changeLabel();
		}

		if (e.getSource() == stop) {
			// stopwatch off
			on = false;
		}
	}
}