Why I can not get .values() from Enum object class?

Question

I want to create universal method, for any enum object, that will check if enum has specified value name, but as Enum type object I am unnable to use method values();. Why?

Is there any way to get values from an Enum type object?

I need method like this to check if value from configuration is a valid string for myEnum.valueOf(String); because if given string will be wrong then it will throw an exception (and I do not want it).

I want my method to look like this:

public static Boolean enumContains(Enum en, String valueString){ return toStringList(en.values()).contains(valueString.toUpperCase()); }

But there is no method Enum.values(). How to create this method correctly?

I want to make it universal, so I put just Enum as type of argument to match any Enum object to this method. — Albert451
– Albert451, Commented Dec 16, 2018 at 17:28
And values does only work for the enum type, e.g. MyEnum.values() but clearly not for a specific value of an enum like in your method... — UninformedUser
– UninformedUser, Commented Dec 16, 2018 at 17:29
ok, that can't work for any enum as explained by the others in the comment — UninformedUser
– UninformedUser, Commented Dec 16, 2018 at 17:29
Reflection would also be a workaround, but who wants to use reflection...getDeclaredField("$VALUES"); or Enum.class.getDeclaredMethod("values"); for the enum class — UninformedUser
– UninformedUser, Commented Dec 16, 2018 at 17:31

Jacob G. · Accepted Answer · 2018-12-16 17:33:22Z

Enum#values is a method that is generated by the compiler, so you cannot use it at compile time unless you pass in a specific enum and not Enum<?>.

See: https://stackoverflow.com/a/13659231/7294647

One solution would be to pass in a Class<E extends Enum<E>> instead and use Class#getEnumConstants:

public static <E extends Enum<E>> Boolean enumContains(Class<E> clazz, String valueString){ return toStringList(clazz.getEnumConstants()).contains(valueString.toUpperCase()); }

If you have an enum named MyEnum, then you can simply pass in MyEnum.class as the first argument.

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