How to get Enum Value from index in Java

Question

I have an enum in Java   public enum Months       JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC     I want to access enum values by index  e g   Months 1    JAN  Months 2    FEB        How shall I do that

User · Answer

Here s three ways to do it   public enum Months       JAN 1   FEB 2   MAR 3   APR 4   MAY 5   JUN 6   JUL 7   AUG 8   SEP 9   OCT 10   NOV 11   DEC 12         int monthOrdinal   0       Months int ord            this monthOrdinal   ord             public static Months byOrdinal2ndWay int ord            return Months values   ord-1      less safe            public static Months byOrdinal int ord            for  Months m   Months values                  if  m monthOrdinal    ord                    return m                                  return null            public static Months   MONTHS INDEXED   new Months     null  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC           import static junit framework Assert assertEquals   import org junit Test   public class MonthsTest     Test public void test indexed access         assertEquals Months MONTHS INDEXED 1   Months JAN       assertEquals Months MONTHS INDEXED 2   Months FEB        assertEquals Months byOrdinal 1   Months JAN       assertEquals Months byOrdinal 2   Months FEB         assertEquals Months byOrdinal2ndWay 1   Months JAN       assertEquals Months byOrdinal2ndWay 2   Months FEB

User · Answer

Try this  Months values   index

User · Answer

I just tried the same and came up with following solution   public enum Countries       TEXAS      FLORIDA      OKLAHOMA      KENTUCKY       private static Countries   list   Countries values         public static Countries getCountry int i            return list i              public static int listGetLastIndex             return list length - 1            The class has it s own values saved inside an array  and I use the array to get the enum at indexposition  As mentioned above arrays begin to count from 0  if you want your index to start from  1  simply change these two methods to   public static String getCountry int i        return list  i - 1       public static int listGetLastIndex         return list length      Inside my Main I get the needed countries-object with   public static void main String   args       int i   Countries listGetLastIndex       Countries currCountry   Countries getCountry i       which sets currCountry to the last country  in this case Countries KENTUCKY   Just remember this code is very affected by ArrayOutOfBoundsExceptions if you re using hardcoded indicies to get your objects

User · Answer

I recently had the same problem and used the solution provided by Harry Joy   That solution only works with with zero-based enumaration though  I also wouldn t consider it save as it doesn t deal with indexes that are out of range   The solution I ended up using might not be as simple but it s completely save and won t hurt the performance of your code even with big enums   public enum Example        UNKNOWN 0   unknown    ENUM1 1   enum1    ENUM2 2   enum2    ENUM3 3   enum3         private static HashMap lt Integer  Example gt  enumById   new HashMap lt  gt         static           Arrays stream values    forEach e - gt  enumById put e getId    e               public static Example getById int id            return enumById getOrDefault id  UNKNOWN              private int id      private String description       private Example int id  String description            this id   id          this description  description             public String getDescription             return description             public int getId             return id            If you are sure that you will never be out of range with your index and you don t want to use UNKNOWN like I did above you can of course also do   public static Example getById int id            return enumById get id

[java] How to get Enum Value from index in Java?

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