Resetting the time part of a timestamp in Java

Question

In Java, given a timestamp, how to reset the time part alone to 00:00:00 so that the timestamp represents the midnight of that particular day ?

In T-SQL, this query

Answer 1

Assuming your "timestamp" is a java.util.Date, which is represented as the number of milliseconds since the beginning of the epoch (Jan 1, 1970), you can perform the following arithmetic:

public static Date stripTimePortion(Date timestamp) {
    long msInDay = 1000 * 60 * 60 * 24; // Number of milliseconds in a day
    long msPortion = timestamp.getTime() % msInDay;
    return new Date(timestamp.getTime() - msPortion);
}