convert date from "2009-12 Dec" format to "31-DEC-2009"

Question

'2009-12 Dec' should be converted to '31-DEC-2009'
'2010-09 Sep' should be converted to '30-SEP-2010'
'2010-02 Feb' should be converted to '28-FEB-2010'
'2008-02 Feb' should be converted to '29-FEB-2008'

The values 2009-12 Dec, 2008-02 Feb will be displayed to the User in a drop down. The User have no option to select the DAY.

The user selected value should be passed to the Database. But the database expects the date in the format DD-MMM-YYYY. The query has '<= USER_DATE' condition. So, the last day of the month should be automatically selected and passed to the database.

Pl help me in writing the function that does the above job.

static SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM MMM");

    public static String convertMapedToSqlFormat(final String maped) {
        String convertedMaped = null;
        //....
        return convertedMaped;
    }

    @Test
    public void testConvertMapedToSqlFormat() {
        String[] mapedValues = { "2009-12 Dec", "2009-11 Nov", "2009-10 Oct",
                "2009-09 Sep", "2009-08 Aug", "2009-07 Jul", "2009-06 Jun",
                "2009-05 May", "2009-04 Apr", "2009-03 Mar", "2009-02 Feb",
                "2009-01 Jan", "2008-12 Dec", "2008-11 Nov", "2008-10 Oct" };
        for (String maped : mapedValues) {
            System.out.println(convertMapedToSqlFormat(maped));
        }
    }

Answer 1

Convert it to Calendar and use Calendar#getActualMaximum() to obtain last day of month and set the day with it.

Kickoff example:

String oldString = "2009-12 Dec";
Calendar calendar = Calendar.getInstance();
calendar.setTime(new SimpleDateFormat("yyyy-MM").parse(oldString)); // Yes, month name is ignored but we don't need this.
calendar.set(Calendar.DATE, calendar.getActualMaximum(Calendar.DATE));
String newString = new SimpleDateFormat("dd-MMM-yyyy").format(calendar.getTime()).toUpperCase();
System.out.println(newString); // 31-DEC-2009

Answer 2

• Use your DateFormat (but fix it to yyyy-dd MMM) to parse the date
• convert the Date to Calendar
• Use Calendar.getActualMaximim()
• use dd-MMM-yyyy to format the obtained date.
• call .toUpperCase()

So:

static SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM MMM");
static SimpleDateFormat dbDateFormat = new SimpleDateFormat("yyyy-MMM-dd");

public static String convertMapedToSqlFormat(final String maped) {
    Date date = dateFormat.parse(mapped);
    Calendar cal = Calendar.getInstance();
    cal.setTime(date);
    cal.set(Calendar.DAY_OF_MONTH, cal.getActualMaximum(Calendar.DAY_OF_MONTH));
    return dbDateFormat.format(cal.getTime()).toUpperCase();
}

A few notes:

• if possible use joda-time DateTime
• avoid having strict date formats in the database.