How to check validity of Date String ?

Question

In my project I need to check if a date string evaluates to a proper Date object. I've decided to allow yyyy-MM-dd, and Date formats [(year, month, date) and (year, month, date, hrs, min)]. How can I check if they're valid ? My code returns null for "1980-01-01" and some strange dates (like 3837.05.01) whon giving a string separated by commas :

private Date parseDate(String date){
    Date data = null;

    // yyy-mm-dd
    try {
        DateFormat df = DateFormat.getDateInstance(DateFormat.SHORT);
        df.setLenient(false);
        df.parse(date);
        return data;
    }
    catch (Exception e) {
        try{
            int[] datArr = parseStringForDate(date);
            int len = datArr.length;
            // year, month, day
            if(len == 3){
                return new Date(datArr[0], datArr[1], datArr[2]);
            }
            // year, montd, day, hours, mins
            else if(len ==5){
                return new Date(datArr[0], datArr[1], datArr[2], datArr[3], datArr[4]);
            }
            // year, month, day, hours, mins, secs
            else if(len == 6){
                return new Date(datArr[0], datArr[1], datArr[2], datArr[3], datArr[4], datArr[5]);
            }
            else {
                return data;
            }
        }
        catch (Exception f){
            return data;
        }
    }
}

private int[] parseStringForDate(String s){
    String[] sArr = s.split(",");
    int[] dateArr = new int[sArr.length];

    for(int i=0; i< dateArr.length; i++){
        dateArr[i] = Integer.parseInt(sArr[i]);
    }

    return dateArr;
}

I remember that I had to subtract 1900 from year date, but I also see that month is different etc, and I'd like to avoid checking every element of my array of ints from date string. Is it possible to parse them automatically in Calendar or date object ?

Answer 1

You are doing this the wrong way. You should use SimpleDateFormat.

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
try {
    Date test = sdf.parse(input);
} catch (ParseException pe) {
   //Date is invalid, try next format
}

Answer 2

You can construct SimpleDateFormat objects for your different String formats like this (returning null if the parameter cannot be parsed as a valid date):

// Initializing possibleFormats somewhere only once
SimpleDateFormat[] possibleFormats = new SimpleDateFormat[] {
  new SimpleDateFormat("yyyy-MM-dd"),
  new SimpleDateFormat("yyyy,MM,dd"),
  new SimpleDateFormat("yyyy,MM,dd,HH,mm") };
for (SimpleDateFormat format: possibleFormats)
{
  format.setLenient(false);
}
// initializing ends

public Date parseDate(String date) {
  Date retVal = null;
  int index = 0;
  while (retVal == null && index < possibleFormats.length) {
    try {
      retVal = possibleFormats[index++].parse(date);
    } catch (ParseException ex) { /* Do nothing */ }
  }
  return retVal;
}

Answer 3

Just to show the final outcome, thanks to Csaba_H and Steve Kuo.

private Date parseDate(String date){

    SimpleDateFormat[] possibleFormats = new SimpleDateFormat[] {
        new SimpleDateFormat("yyyy-MM-dd"),
        new SimpleDateFormat("yyyy,MM,dd"),
        new SimpleDateFormat("yyyy,MM,dd,HH,mm") };

    Date retVal = null;
    for (SimpleDateFormat f: possibleFormats) {
        f.setLenient(false);
        try {
            retVal = f.parse(date);
        } catch (ParseException e) {}
    }
    return retVal;
}