Get the difference between two java.sql.Time values

Question

Hi, I'm developping a web application in which I need to to subtract one java.sql,Time value from another. The two values are stored in a database field of type DateTime. I used following code
java.sql.Time start_time=resultset.getTime("startTime");
java.sql.Time end_time=resultset.getTime("startTime");
java.sql.Time diff=start_time-end_time;
can u give me any comment on this code

Answer 1

Remember what the Date/Time object in Java represents - a single point in time.
Subtracting one from another gives you an amount of time elapsed between the two dates. Fine.
Making a new Date out of that number is incorrect. The number no longer represents a point in time, but rather a duration.
Its like saying "There is 10 seconds difference between the two times, so the time is now 1 Jan 1970, 00:00:10 GMT".
The simple and stupid calculation is to take the milliseconds difference, and divide it to get to a more humanly readable value.
// duration in milliseconds
long duration = ?????
long durationInSeconds = duration / 1000;
long durationInMinutes = duration / (60 * 1000);
long durationInHours = duration / (60 * 60 * 1000);
// careful - not always true!
long durationInDays = duration / (24 * 60 * 60 * 1000);
NOTE: The "daysBetween" calculation is potentially complicated by Daylight Time adjustments. The simple approach does not necessarily work exactly.
Cheers,
evnafets