Question

I have the required code for the stopwatch here. All i want is get rid of the Swing part here and display the same output in console. Can anybody help?

import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
import java.text.*;

public class ElapsedTime extends JFrame
{
JLabel time;

long startTime = System.currentTimeMillis();

ElapsedTime()
{
setSize(380,200);
setTitle("http://simpleandeasycodes.blogspot.com/");
setLocation(100,100);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

setLayout(new GridBagLayout());

time = new JLabel("");

time.setFont(new Font("SansSerif",Font.BOLD, 36));

time.setForeground(Color.MAGENTA);

add(time);

//starting new Thread which will update time
new Thread(new Runnable()
{
public void run() 
{ try 
{
updateTime(); 
} 
catch (Exception ie) 
{ }
}
}).start();
}

public void updateTime()
{
try
{
while(true)
{
//geting Time in desire format
time.setText(getTimeElapsed());
//Thread sleeping for 1 sec
Thread.currentThread().sleep(1000);
}
}
catch (Exception e)
{
System.out.println("Exception in Thread Sleep : "+e);
}
}

public String getTimeElapsed()
{
long elapsedTime = System.currentTimeMillis() - startTime;
elapsedTime = elapsedTime / 1000;

String seconds = Integer.toString((int)(elapsedTime % 60));
String minutes = Integer.toString((int)((elapsedTime % 3600) / 60));
String hours = Integer.toString((int)(elapsedTime / 3600));

if (seconds.length() < 2)
seconds = "0" + seconds;

if (minutes.length() < 2)
minutes = "0" + minutes;

if (hours.length() < 2)
hours = "0" + hours;

return minutes+":"+seconds;
}

public static void main(String[] args) 
{
JFrame obj = new ElapsedTime();
obj.setVisible(true);
}
}

Answer 1

The keys are:

a.) Finding which character to write to the console in order to remove the most recently-written character (\b, or \010 in ASCII)
b.) Realising that you need to remember how many characters you’ve written to the console the last time you updated it
c.) Remembering to use print instead of println

public class Test {

  public static void main(String[] args) throws InterruptedException {
    int charsWritten = 0;
    long start = System.currentTimeMillis();
    while (1 > 0) {
      Thread.sleep(1000);
      long elapsedTime = System.currentTimeMillis() - start;
      elapsedTime = elapsedTime / 1000;

      String seconds = Integer.toString((int) (elapsedTime % 60));
      String minutes = Integer.toString((int) ((elapsedTime % 3600) / 60));
      String hours = Integer.toString((int) (elapsedTime / 3600));

      if (seconds.length() < 2) {
        seconds = "0" + seconds;
      }

      if (minutes.length() < 2) {
        minutes = "0" + minutes;
      }

      if (hours.length() < 2) {
        hours = "0" + hours;
      }

      String writeThis = hours + ":" + minutes + ":" + seconds;

      for (int i = 0; i < charsWritten; i++) {
        System.out.print("\b");
      }
      System.out.print(writeThis);
      charsWritten = writeThis.length();
    }
  }
}

Note: you could be more efficient by only clearing the console up to only the characters you are changing but I figure you’re not going to get that much of a speed improvement.