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

问题:

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?

回答1:

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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