creating generic enum wrapper for validations

Question

Disclaimer: not very strong with generics.

enum WeekDays {
   SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY;
}
enum Months {
   JANUARY, FEBRAURY, MARCH, APRIL, MAY, JUNE, JULY, AUGUST, SEPTEMBER, OCTOBER, NOVEMBER, DECEMBER;
}
enum Directions {
   East, West, North, South, Up, Down
}

Let's say I have above enums and there is a service which sends me random Strings.

I need to verify if the targeted String response is a valid enum value or not.

I was thinking of coding of something on lines as below:

static <T> boolean isValidEnum(String value, T enumClass ){
   try {
       enumClass.valueOf(value);
       return true;
   } catch (Exception e) {
   }
   return false;
}

The call would be like:

isValidEnum("TUESDAY", WeekDays)

but line enumClass.valueOf(value); is not happy about my function.

Any pointers is appreciated! TIA

lczapski · Accepted Answer · 2020-05-12 10:10:47Z

2

You can rewrite it to this:

static <T extends Enum<T>> boolean isValidEnum(String value, Class<T> enumClass ){
    try {
        Enum.valueOf(enumClass, value);
        return true;
    } catch (Exception e) {
    }
    return false;
}

and

isValidEnum("TUESDAY", WeekDays.class)

answered May 12, 2020 at 10:10

lczapski

4,1603 gold badges18 silver badges35 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

NoobEditor Over a year ago

simple and elegant, missed the Enum utility completely!

Andrea Ligios Over a year ago

Simple, but not elegant: it throws an exception every time the value is not valid

NoobEditor Over a year ago

@AndreaLigios: IMHO, exceptions if raised consciously are better sometimes than taking the long path of iteration but then again, individual opinion varies!

Andrea Ligios · Accepted Answer · 2020-05-12 10:29:13Z

2

You need to iterate the Enum values and check if there is a match with the value passed:

With Java 8 and newer versions:

static <T> boolean isValidEnum(String value, T enumClass ){
    return Arrays.stream(((Class) enumClass).getEnumConstants())
            .anyMatch(v -> v.toString().equals(value));
}

With older Java versions:

static <T> boolean isValidEnum(String value, T enumClass ){
    for (Object v : ((Class) enumClass).getEnumConstants()){
        if (v.toString().equals(value)) return true;
    }
    return false;
}

edited May 12, 2020 at 10:29

answered May 12, 2020 at 10:11

Andrea Ligios

50.4k29 gold badges127 silver badges256 bronze badges

Comments

Eklavya · Accepted Answer · 2020-05-12 10:33:06Z

1

There is a library for this, you can also use that in case you don't want to implement it.

EnumUtils of org.apache.commons.lang3

EnumUtils.isValidEnum(WeekDays.class, "TUESDAY")

edited May 12, 2020 at 10:33

answered May 12, 2020 at 10:16

Eklavya

18.6k4 gold badges33 silver badges62 bronze badges

2 Comments

NoobEditor Over a year ago

isValidEnum also does the same thing internally what i am trying to do, interest was to understand the under the hood thing!

Eklavya Over a year ago

@NoobEditor Yes I undestand, I just want let you know about the library.

Collectives™ on Stack Overflow

creating generic enum wrapper for validations

3 Answers 3

3 Comments

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

3 Comments

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related