empty array position getting months

Question

Is this a jdk/jre bug? I reported this when jdk7 was released but never received a feedback, is it normal get an array of 13 positions?

String[] months = DateFormatSymbols.getInstance().getMonths();
System.out.println(months.length + " " + Arrays.toString(months));

output: 13 [enero, febrero, marzo, abril, mayo, junio, julio, agosto, septiembre, octubre, noviembre, diciembre, ]

Answer 1

Not a bug. Looking at the javadoc of the source code ( java.text.DateFormatSymbols), it says:

Month strings. For example: "January", "February", etc. An array of 13 strings (some calendars have 13 months), indexed by Calendar.JANUARY, Calendar.FEBRUARY, etc.

String months[] = null;

Also, getWeekdays() method returns 8 values and so on.

public final static int JANUARY = 0;
public final static int FEBRUARY = 1;
public final static int MARCH = 2;
public final static int APRIL = 3;
public final static int MAY = 4;
public final static int JUNE = 5;
public final static int JULY = 6;
public final static int AUGUST = 7;
public final static int SEPTEMBER = 8;
public final static int OCTOBER = 9;
public final static int NOVEMBER = 10;
public final static int DECEMBER = 11;
public final static int UNDECIMBER = 12;

The API describes UNDECIMBER as: field indicating the thirteenth month of the year. Although GregorianCalendar does not use this value, lunar calendars do.

Read here for such calendars.