I thought enum was also a java collection. This make it more simple than using ArrayList tho.

package com.codegym.task.task08.task0828; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.ArrayList; import java.util.HashSet; import java.util.HashMap; import java.util.List; import java.util.Set; /* Month number */ public class Solution { enum Month{ January, February, March, April, May, June, July, August, September, October, November, December } public static void main(String[] args) throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String monthName = reader.readLine(); Month month = Month.valueOf(monthName); System.out.println(monthName + " is month "+(month.ordinal() + 1)); } }