I often find the need for a stop watch, so I wrote an application for one. This code has several interesting salient points for java beginners. It shows a number of little tricks for customizing an application and addresses the use of the Swing Timer widget.
This jar file is an executable. In windows, where you have Java installed, download the file, then just click on it with the mouse to run it. Or to run it in place, right click and choose to open the file where it is.
Feel free to download and use this timer
StopWatch source Note: my provider will not download .java files so this is in .txt format. Also, the current StopWatch.jar displays hundredths of seconds but this is a trivial addition.
Because the code is over documented for java beginners, I have included it here instead of making a separate explaination
/**
* @(#)StopWatch.java
*
* StopWatch application
*
* This stop watch keeps track of time (up to hours not days) allowing the user
* to start, stop, pause and resume the watch.
*
* This program can be used as the basis for updating a component
* in a larget program based on elapsed time. i. e. You can replace the label
* update in the Timer action listener with a different component.
*
* The heart of the program is a java Swing widget called Timer.
* Timer is threaded and works in the background.
*
* Threads can be started, stopped and interruped and simulate parallel processing
* by sharing the CPU with other processes.
*
* @author Kenneth L Moore Professor CCAC
* @version 1.00 2011/5/11
*/
// for windowing
import java.awt.*;
// For the swing Timer
import javax.swing.Timer;
// for the JFrame, JButton, JLable components
import javax.swing.*;
// misc
import java.util.*;
// For the action listeners which allow buttons
// to respond to events.
// And which allows the Timer to communicate
// at a designated time interval.
import java.awt.event.*;
// JFrame gives the program windowing capability.
// ActionListener allows communication through events
public class StopWatch extends JFrame implements ActionListener{
/*
* Global variables needed to reference data in multiple
* parts of the class.
*/
// The component that shows the elapsed time.
private JLabel displayTimeLabel;
// The variables that keep track of start and stopTimerButton
private long watchStart, watchEnd;
// The Threaded Swing widget
private Timer theChronometer;
// Keeps track of time when pausing the Timer.
private long pausedTime;
// Lets the program know if starting or resuming
private boolean paused = false;
// Button that changes from "Start" to "Resume" depending on pause status.
private JButton activateTimerButton;
// run the program
public static void main(String[] args) {
// instantiate (create an instance in memory) a stop watch
StopWatch s = new StopWatch();
// by default frames are not visible
s.setVisible(true);
// center in window
s.setLocationRelativeTo(null);
}
// default constructor, easily identified as such because it has no return type
// and no parameters.
public StopWatch(){
// initialize
super();
setSize(400,150);
setLayout(new GridLayout(2,1));
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setTitle("Stop Watch: Professor Kenneth Moore CCAC");
// layout a display with a label at the top to display elapsed time
// and a row of buttons to control the timer
// define some fonts
Font largeFontBOLD = new Font("Calibri", Font.BOLD,20);
Font largeFontPLAIN = new Font("Calibri", Font.PLAIN,20);
JPanel buttonPanel = new JPanel();
buttonPanel.setLayout(new GridLayout(1,3));
activateTimerButton = new JButton("Start");// will display resume when the watch is paused
JButton stopTimerButton = new JButton("Stop");
JButton pauseTimerButton = new JButton("Pause");
// register buttons to generate events when clicked
activateTimerButton.addActionListener(this);
stopTimerButton.addActionListener(this);
pauseTimerButton.addActionListener(this);
// the display for elapsed time
displayTimeLabel = new JLabel("Stop Watch Application");
displayTimeLabel.setHorizontalAlignment(JLabel.CENTER);
// use a large font
displayTimeLabel.setFont(largeFontPLAIN);
activateTimerButton.setFont(largeFontBOLD);
stopTimerButton.setFont(largeFontBOLD);
pauseTimerButton.setFont(largeFontBOLD);
//The JLabel background is transparent by default,
//so changing the background color doesn't anything.
//Set to Opaque to make visible
displayTimeLabel.setOpaque(true);
// The default colors available are often too "loud".
// For example Color.yellow is very bright but my gold is more subtle.
// by controling the Red, Blue and Green intensity
// you can make up to 256 cubed or 16,777,216 custom colors.
displayTimeLabel.setBackground(new Color(255,204,51));// gold
displayTimeLabel.setForeground(new Color(153,0,0));// burgundy
stopTimerButton.setBackground(new Color(0,150,0));// dark green
stopTimerButton.setForeground(new Color(255,204,51));
activateTimerButton.setBackground(new Color(0,150,0));
activateTimerButton.setForeground(new Color(255,204,51));
pauseTimerButton.setBackground(new Color(0,150,0));
pauseTimerButton.setForeground(new Color(255,204,51));
// add the components to the layout
buttonPanel.add(activateTimerButton);
buttonPanel.add(stopTimerButton);
buttonPanel.add(pauseTimerButton);
add(displayTimeLabel);
add(buttonPanel);
/*
* The following code instantiates (creates an instance in memory) a Swing timer.
*
* If you have never seen code like this, it looks odd at first.
*
* What is being done is:
*
* theChronometer = new Timer(1000, someActionListener);
*
* where 1000 is a delay of 1000 miliseconds or 1 second and insead of
* defining someActionListener (which will get an event every second) in
* a separate part of the code, we define it inline.
*
*/
theChronometer =
new Timer(1000,new ActionListener(){
public void actionPerformed(ActionEvent e){
int seconds = (int)(System.currentTimeMillis()-watchStart)/1000;
int days = seconds / 86400;
int hours = (seconds / 3600) - (days * 24);
int min = (seconds / 60) - (days * 1440) - (hours * 60);
int sec = seconds % 60;
String s = new String(""+hours+" hours "+min+ " min "+sec+" sec");
displayTimeLabel.setText(s);
}
});
}
// action performed for the button events
public void actionPerformed(ActionEvent e){
// invoke the Timer Thread stop command
if(e.getActionCommand().equals("Stop")){theChronometer.stop();}
// either start the Timer Thread at zero or pick up where paused.
else if(e.getActionCommand().equals("Start") || e.getActionCommand().equals("Resume")){
if(!paused){
watchStart = System.currentTimeMillis();
theChronometer.start();
}
else{
watchStart = System.currentTimeMillis()+pausedTime;
pausedTime = 0;
theChronometer.start();
paused = false;
// set the button display to Start, it may have been Resume
activateTimerButton.setText("Start");
}
}
// there is no pause for Timer so we kludge one
else if(e.getActionCommand().equals("Pause")){
long now = System.currentTimeMillis();
pausedTime -= (now - watchStart);
theChronometer.stop();
paused = true;
// set the button display to Resume instead of Start
activateTimerButton.setText("Resume");
}
}
}