CODEWITHSUNDEEP
java
Darth Blue Ray
Darth Blue Ray

Reputation: 9745

Time problem with this code 

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

public class test {

    /*
     * Calculate the difference between two date/times   * 
     * 
     */

    private static long dateDiff(Date toDate, Date fromDate) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(toDate);
        long ms = cal.getTimeInMillis();
        cal.setTime(fromDate);
        ms -= cal.getTimeInMillis();
        return ms;
    }

    public static void main(String[] args) {

        SimpleDateFormat sdf = new SimpleDateFormat("hh:mm:ss");
        Date d1 = null;
        Date d2 = null;

        try {
            d1 = sdf.parse("11:00:00");
            d2 = sdf.parse("10:00:00");
        } catch (Exception e) {
            e.printStackTrace();
        }

        long result = dateDiff(d1, d2);

        Date time = new Date(result);

        System.out.println(time);
    }
}

When I run it I get this result :

Thu Jan 01 02:00:00 CET 1970

I would expect 1 hour difference ?! again a problem with Timezone??

Any idea how I can fix it.

thx all

Upvotes: 0

Views: 232

Answers (4)

Stephen C
Stephen C

Reputation: 718986

I don't know what you expect this to do, but what you are actually doing is outputting the date corresponding to one hour after midnight on Jan 1 1970, using the default timezone.

You seem to want to Date to represent a duration (i.e. a number of seconds). It doesn't do that, and neither will the Date formatters render a Date as a duration.

I need the time difference between two Date fields and then put it in MySql (time format)

For what you are trying to do, you need calculate the duration value as a long, then use the java.sql.Time(long) constructor to create a Time object. You can either serialize this object using its toString() method or use it as a parameter in a JDBC prepared statement.

It turns out that my advice above is incorrect too.

Your real problem is that the SQL Time type is for representing times ... not durations. In fact, SQL does not have a dedicated duration type, so the best you can do is represent the duration as an integer number of seconds or milliseconds or whatever.

(For the more general case, the Joda Time libraries are generally thought to provide the best APIs for manipulating dates, times and related temporal values. But for this simple case, the standard J2SE libraries should suffice ... provided that you use them correctly.)

Upvotes: 3

samarjit samanta
samarjit samanta

Reputation: 1315

Hi try this setting timezone to GMT. Remove day, month in words in the resultant time difference. This method does nothing but assumes these many milliseconds since starting of time counter in java, which is 1st Jan 1970. So if your result says 3rd Jan 1970 means 3 days have passed since time counter started, which is perfect. You just need to interpret it properly, but formatting your answer 

...
long result = dateDiff(d1, d2); //This is your code in main([])
SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss SSS");
dateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
System.out.println(dateFormat.format(new Date(result )));

Upvotes: 0

Alp
Alp

Reputation: 29739

Why don't you just take the milliseconds of both dates and substract them from each other?

Calendar cal = Calendar.getInstance();
cal.setTime(d1);
long d1ms = cal.getTimeInMillis();
cal.setTime(d2);
long d2ms = cal.getTimeInMillis();

long diffMs = d1ms - d2ms;
long diffHour = diffMs * 1000 * 60 * 60;

Upvotes: 1

Marcelo
Marcelo

Reputation: 11308

The problem is that a difference of two Date types can not be represented by another Date type.

Upvotes: 2

Related Questions