Date vs TimeStamp vs calendar?

by

java.sql.Timestamp A thin wrapper around java.util.Date that allows the JDBC API to identify this as an SQL TIMESTAMP value.

If you check java.sql.Timestamp JavaDoc, it is very explicit that this class extends from java.util.Date (as java.sql.Date does). And in real world projects you must plain java.util.Date when storing the data in your database and mostly java.sql.Timestamp since it stores date and time value, while java.sql.Date just stores date value.

On the other hand, java.util.Calendar is abstract since there are more implementations of this apart from java.util.GregorianCalendar. If you see the code of Calendar#getInstance from HotSpot, you will see that it calls createCalendar(TimeZone.getDefaultRef(), Locale.getDefault(Locale.Category.FORMAT)), and this method code uses 3 different calendars: BuddhistCalendar, JapaneseImperialCalendar and GregorianCalendar. This code is copied from JDK 7 source:

private static Calendar createCalendar(TimeZone zone,
                                       Locale aLocale) {
    Calendar cal = null;

    String caltype = aLocale.getUnicodeLocaleType("ca");
    if (caltype == null) {
        // Calendar type is not specified.
        // If the specified locale is a Thai locale,
        // returns a BuddhistCalendar instance.
        if ("th".equals(aLocale.getLanguage())
                && ("TH".equals(aLocale.getCountry()))) {
            cal = new BuddhistCalendar(zone, aLocale);
        } else {
            cal = new GregorianCalendar(zone, aLocale);
        }
    } else if (caltype.equals("japanese")) {
        cal = new JapaneseImperialCalendar(zone, aLocale);
    } else if (caltype.equals("buddhist")) {
        cal = new BuddhistCalendar(zone, aLocale);
    } else {
        // Unsupported calendar type.
        // Use Gregorian calendar as a fallback.
        cal = new GregorianCalendar(zone, aLocale);
    }

    return cal;
}

Now, why to work directly with Calendar instead of GregorianCalendar? Because you must work with abstract classes and interfaces when provided instead of working directly with implementations. This is better explained here: What does it mean to “program to an interface”?

Apart from this, if you will work with date and times, I recommend using a library like Joda-Time that already handles and solves lot of the problems with the current Java Date API and also provides methods to retrieve this date and times object in java.util.Date flavor.

More Related Contents:

  1. Why is subtracting these two times (in 1927) giving a strange result?
  2. How to calculate remaining days of the month? [duplicate]
  3. Converting ISO 8601-compliant String to java.util.Date
  4. Why is the Java date API (java.util.Date, .Calendar) such a mess?
  5. display Java.util.Date in a specific format
  6. How to determine day of week by passing specific date?
  7. Is java.sql.Timestamp timezone specific?
  8. java.text.ParseException: Unparseable date: java.text.DateFormat.parse(DateFormat.java:579)
  9. “EEE MMM dd HH:mm:ss ZZZ yyyy” date format to java.sql.Date
  10. Date format Mapping to JSON Jackson
  11. Parsing ISO 8601 date format like 2015-06-27T13:16:37.363Z in Java [duplicate]
  12. Calculate elapsed time in Java / Groovy
  13. Changing String date format
  14. System.currentTimeMillis() vs. new Date() vs. Calendar.getInstance().getTime()
  15. SimpleDateFormat parse loses timezone [duplicate]
  16. Should I use java.util.Date or switch to java.time.LocalDate
  17. How to get start and end range from list of timestamps?
  18. Why were most java.util.Date methods deprecated?
  19. java date problem in parsing
  20. How to properly format the date?
  21. Java Timestamp – How can I create a Timestamp with the date 23/09/2007?
  22. Changing Java Date one hour back
  23. A good date converter for Jalali Calendar in Java? [closed]
  24. Date format conversion Android
  25. java sql date time
  26. how to convert long date value to mm/dd/yyyy format [duplicate]
  27. How to compare two string dates in Java?
  28. calculate business days including holidays
  29. Parse time of format hh:mm:ss [closed]
  30. Java SimpleDateFormat pattern for W3C XML dates with timezone [duplicate]

Leave a Comment