Suppose you wanted to write a program which prints the current month of the year. You could define a constant for each month, then assign one of the constants to a variable. You could also define an array of string references containing the name of each month.

Listing 1 - MonthsDriver.java (version 1)

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

    public final static String[] months =
    {
        "JANUARY","FEBRUARY","MARCH","APRIL","MAY","JUNE",
        "JULY","AUGUST","SEPTEMBER","OCTOBER","NOVEMBER","DECEMBER"
    };
   
    public static void main(String[] args)
    {
        byte month = MAY;
        System.out.println(months[month]);                // Prints MAY
    }
}

The program in Listing 1 works, but what if you had initialized the variable month as follows?

byte month = 20;