Thread: Date and SimpleDateFormat Class

import java.text.SimpleDateFormat;
import java.util.Date;

public class Time_Difference{

public static void main(String[] args) {

String dateStart = "01/15/2012 09:29:58";
String dateStop = "01/15/2012 10:29:58";

//HH converts hour in 24 hours format (0-23), day calculation
SimpleDateFormat format = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss");

Date d1 = null; //Doubt here...
Date d2 = null;

try {
d1 = format.parse(dateStart);
d2 = format.parse(dateStop);

//in milliseconds
long diff = d2.getTime() - d1.getTime();

long diffSeconds = diff / 1000 % 60;
long diffMinutes = diff / (60 * 1000) % 60;
long diffHours = diff / (60 * 60 * 1000) % 24;
long diffDays = diff / (24 * 60 * 60 * 1000);

System.out.print(diffDays + " days, ");
System.out.print(diffHours + " hours, ");
System.out.print(diffMinutes + " minutes, ");
System.out.print(diffSeconds + " seconds.");

} catch (Exception e) {
e.printStackTrace();
}

}




I have 3 questions in the above code block

1) why do we assign null to the Date variables d1 & d2?
2)What exactly does does d1 and d2 return after the executing the following lines of code?
d1 = format.parse(dateStart);
d2 = format.parse(dateStop);
I know we are converting date string to some integer value ...But what exactly is that value??

3] please explain the below logic of how the diff between d1 & d2 is converted into seconds,minutes, hours etc..
long diffSeconds = diff / 1000 % 60;
long diffMinutes = diff / (60 * 1000) % 60;
long diffHours = diff / (60 * 60 * 1000) % 24;
long diffDays = diff / (24 * 60 * 60 * 1000);



Thank you i really appreciate ur time and support....It means a lot for a beginner like me

You were given a link to the general forum guidelines in your first post that included instructions on how to post code correctly. Please review those instructions and post your code correctly with code or highlight tags.

Thank u andbin ... I understood the logic and the code as well .. Thanks a lot