Format Number as Date

[aminur rashid]

Hello
I have a problem in SimpleDateFormatter and it will be nice if any one help me.
As we know a user can set any valid format to a SimpleDateFormatter.e.g "mm d", "MM/dd/yy" etc.
Now I want that if I have set a format to a SimpleDateFormatter (say "MM/dd:yy")and if I pass a string of numbers say "123456" it should format the string in the specified format.(ie. 12 should be taken as month 34 should be taken as day (can convert 34 to 30+4 or can throw error.))Similar to what MS Excel does when we set format of a cell of MS excel to DateFormat.
Well DateaFormatter expects the input to be formatted in the same pattern as that was set (i.e if we have set the pattern as "MM d:yy" it expects value as 11:11:11 to format else it will trhow exception)
Any suggestions, ideas is welcome.

[Joel McNary]

A couple ideas come to mind:
1). Have a whole bunch of SimpleDateFormats -- one for each expected input format.
Set up a series of regexes and compare the input string to them to see which SimpleDateFormat to use.
2). Write your own DateFormat that ignores all non-digit characters. It would then translate the string as described. Thus, 12/25/04 12.25.04, 12-25-04, 122504, 12-25-2004, etc., would all be translated the same way.
I wrote the following Java version of option 2 several years ago (it was based on an some Objective-C code that was used to do the same thing)
Please note that this is not the whole class, just the sample methods.

    /**
     * DOCUMENT ME!
     *
     * @param aDateString DOCUMENT ME!
     *
     * @return DOCUMENT ME!
     */
    public Calendar parseDateString(String aDateString){
        Calendar aDate;
        int year;
        int month;
        int day;
        int hour;
        int minute;
        int second;
        int length;
        int currentPosition;
        int stringPosition;
        Value currentInt;
        boolean shouldBreak;
        currentInt = new Value();
        year = 0;
        month = 0;
        day = 0;
        hour = 0;
        minute = 0;
        second = 0;
        stringPosition = 0;
        length = aDateString.length();
        currentPosition = 0;
        while (stringPosition < length){
            stringPosition += this.getNextNumberFromStringAtPosition(aDateString, stringPosition, currentInt);
            shouldBreak = false;
            switch (currentPosition){
            default:
                shouldBreak = true;
                break;
            case 0:
                month = currentInt.getIntValue();
                break;
            case 1:
                day = currentInt.getIntValue();
                break;
            case 2:
                year = currentInt.getIntValue();
                if (stringPosition < length){
                    if ((aDateString.charAt(stringPosition) >= '0') && (aDateString.charAt(stringPosition) <= '9')){
                        stringPosition += this.getLastOfYear(aDateString, stringPosition, year, currentInt);
                        year = currentInt.getIntValue();
                    }
                }
                break;
            case 3:
                hour = currentInt.getIntValue();
                break;
            case 4:
                minute = currentInt.getIntValue();
                break;
            case 5:
                second = currentInt.getIntValue();
                break;
            }
            ++currentPosition;
            if (shouldBreak){
                break;
            }
        }
        aDate = Calendar.getInstance();
        aDate.clear();
        //Have to set to month -1 because months are zero indexed
        aDate.set(year, (month - 1), day, hour, minute, second);
        return aDate;
    }
    
     /**
     * DOCUMENT ME!
     *
     * @param aString DOCUMENT ME!
     * @param aPosition DOCUMENT ME!
     * @param year DOCUMENT ME!
     * @param currentInt DOCUMENT ME!
     *
     * @return DOCUMENT ME!
     */
    public int getLastOfYear(String aString, int aPosition, int year, Value currentInt){
        int charA;
        int charB;
        int index;
        int length;
        int result;
        int count;
        int targetCount;

        count = 0;
        length = aString.length();
        index = aPosition;

        charA = -1;

        while (index < length){
            charA = aString.charAt(index);
            ++index;
            ++count;

            if ((charA >= '0') && (charA <= '9')){
                break;
            }

            charA = -1;
        }

        if (charA == -1){
            currentInt.setIntValue(0);

            return length;
        }

        result = year * 10;
        result += (int) (charA - '0');

        if (index < length){
            charB = (char) aString.charAt(index);

            if ((charB >= '0') && (charB <= '9')){
                ++count;
                result *= 10;
                result += (int) (charB - '0');
            }
        }

        currentInt.setIntValue(result);

        return count;
    }

    /**
     * DOCUMENT ME!
     *
     * @param aString DOCUMENT ME!
     * @param aPosition DOCUMENT ME!
     * @param returnInt DOCUMENT ME!
     *
     * @return DOCUMENT ME!
     */
    public int getNextNumberFromStringAtPosition(String aString, int aPosition, Value returnInt){
        int charA;
        int charB;
        int index;
        int length;
        int count;
        int targetCount;
        StringBuffer aBuffer;
        Integer anInt;

        //int result;
        aBuffer = new StringBuffer();

        count = 0;
        length = aString.length();
        index = aPosition;

        charA = -1;

        while (index < length){
            charA = aString.charAt(index);
            ++index;
            ++count;

            if ((charA >= '0') && (charA <= '9')){
                break;
            }

            charA = -1;
        }

        if (charA == -1){
            returnInt.setIntValue(0);

            return length;
        }

        aBuffer.append((char) charA);

        //result = (int)(charA - '0');
        if (index < length){
            charB = (char) aString.charAt(index);

            if ((charB >= '0') && (charB <= '9')){
                ++count;

                //result *= 10;
                //result += (int)(charB - '0');
                aBuffer.append((char) charB);
            }
        }

        try{
            anInt = new Integer(aBuffer.toString());
        }
        catch (NumberFormatException e){
            anInt = new Integer(0);
        }

        returnInt.setIntValue(anInt.intValue());

        return count;
    }

[ September 23, 2003: Message edited by: Joel McNary ]