Determine if a String is a valid date before parsing

Question

I have this situation where I am reading about 130K records containing dates stored as String fields. Some records contain blanks (nulls), some contain strings like this: \'

Answer 1

Assuming the patterns you gave are the only likely choices, I would look at the String passed in to see which format to apply.

public Date parseDate(final String date) {
  if (date == null) {
    return null;
  }

  SimpleDateFormat format = (date.charAt(2) == '/') ? new SimpleDateFormat("dd/MMM/yyyy")
                                                   : new SimpleDateFormat("dd-MMM-yy");
  try {
    return format.parse(date);
  } catch (ParseException e) {
    // Log a complaint and include date in the complaint
  }
  return null;
}

As others have mentioned, if you can guarantee that you will never access the DateFormats in a multi-threaded manner, you can make class-level or static instances.