Computing the name of the month

I created the following program that transforms a numerical month into the corresponding textual month. I initially calculated the starPoint and endPoint in the class constructor; then I changed that calculation to the getName method. Which is a better option? Calculating in the class constructor, or in a separate method like shown in the code?

/**
 * Created by Robert Holland on 25/11/2016.
 *
 * A class that accepts a number and calculates
 * the corresponding month. Once the month has
 * been calculated it will then be returned.
 *
 */

public class Month
{
    public static final String MONTHS = "January   " + "February  " + "March     " +
                                        "April     " + "May       " + "June      " +
                                        "July      " + "August    " + "September " +
                                        "October   " + "November  " + "December  ";
    private int monthNumber;

    //Construct a month class that has a value equal to the numerical month
    //@param uMonthNumber the number of the month to find the correspondance.
    public Month(int uMonthNumber)
    {
        monthNumber = uMonthNumber;
    }

    //Determine the name that corresponds to the month number.
    //@return month the name of the corresponding month.
    public String getName()
    {
        String month;
        int startPoint;
        int endPoint;

        endPoint = monthNumber * 10;
        startPoint = endPoint - 10;
        month = MONTHS.substring(startPoint, endPoint);

        return month;
    }
}

This exists already:

It's not the prettiest to use but it's there.

import java.time.*;
import java.time.format.*;
import java.util.*;

public class Example {

    public static void main(String[] args) {
        Month month = Month.of(2);
        System.out.printf("%s", month.getDisplayName(TextStyle.FULL, new Locale("en")));
        // outputs:
        // February
    }
}

Don't re-write code that's in your standard libraries :)

StackExchange Code Review Q#148112, answer score: 3