Get month number from month name

Question

I have this.

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    String monthName = br.readLine();

How to get mon

Answer 1

Another approach using java.text.DateFormatSymbols is this:

public static int monthAsNumber(
  String  month,
  Locale  locale,
  boolean abbreviated,
  boolean caseInsensitive
) {
  DateFormatSymbols dfs = new DateFormatSymbols(locale);
  String[] months = (abbreviated ? dfs.getShortMonths() : dfs.getMonths());

  if (caseInsensitive) {
    for (int i = 0; i < 12; i++) {
      if (months[i].equalsIgnoreCase(month)) {
        return i; // month index is zero-based as usual in old JDK pre 8!
      }
    }
  } else {
    for (int i = 0; i < 12; i++) {
      if (months[i].equals(month)) {
        return i; // month index is zero-based as usual in old JDK pre 8!
      }
    }
  }
  return -1; // no match
}

The proposed signature of seach method illustrates the many possible variations. Example:

System.out.println(monthAsNumber("MÄRZ", Locale.GERMANY, false, true));
// output: 2 (zero-based!)

If you want a month number starting with 1 then just add 1 to the result (more intuitive and also my recommendation).

Starting with Java 8 you have a new variation, too, namely stand-alone months. While in English these month names are identical in other languages they are not always identical (for example in Czech language "leden" (January) instead of "ledna"). To achieve these stand-alone forms you can use Month.getDisplayName(...) (not tested):

public static int monthAsNumber(
  String  month,
  Locale  locale,
  boolean abbreviated,
  boolean caseInsensitive,
  boolean standAlone
) {
  TextStyle style;
  Month[] months = Month.values[];

  if (abbreviated) {
    style = standAlone ? TextStyle.SHORT_STANDALONE : TextStyle.SHORT;
  } else {
    style = standAlone ? TextStyle.FULL_STANDALONE : TextStyle.FULL;
  }

  if (caseInsensitive) {
    for (int i = 0; i < 12; i++) {
      if (months[i].getDisplayName(style, locale).equalsIgnoreCase(month)) {
        return i; // month index is zero-based as usual in old JDK pre 8!
      }
    }
  } else {
    for (int i = 0; i < 12; i++) {
      if (months[i].getDisplayName(style, locale).equals(month)) {
        return i; // month index is zero-based as usual in old JDK pre 8!
      }
    }
  }
  return -1; // no match
}