generic Enum.valueOf method : Enum class in parameter and return Enum item

Question

I'd like to make a method that implement valueOf on any Enum class passed in parameter (and also wrap some specialized error/missing-name code). So basically, I have several Enum such as:

enum Enum1{ A, B, C }
enum Enum2{ D, E, F }

And I want a method that wrap around valueOf. I could not find a way to directly pass an Enum class in parameter on which I could call valueOf. Here is what I came up with:

private static Enum getEnum(Class<Enum> E, String name){
    for(Enum e: E.getEnumConstants())
        if(e.name().equals(name)){
            return e;
        }
    return null;
}

Which I want to call with: getEnum(Enum1,"A"). But it does not like it:

java: cannot find symbol
  symbol:   variable Enum1
  location: class Main

isn't there a method for that - Enum.valueOf(Enum1.class, value);? — EpicPandaForce
– EpicPandaForce, Commented Oct 14, 2014 at 9:44

EpicPandaForce · Accepted Answer · 2014-10-15 09:59:57Z

9

Why implement your own, when you can use Java's own implementation for this?

 YourEnum yourEnum = Enum.valueOf(YourEnum.class, value);

http://docs.oracle.com/javase/7/docs/api/java/lang/Enum.html#valueOf(java.lang.Class,%20java.lang.String)

Your method then becomes:

private static <E extends Enum<E>> E getEnum(Class<E> enumClass, String name){
    try {
        return Enum.valueOf(enumClass, name);
    } catch(IllegalArgumentException e) {
        return null;
    }
}

and you can call it with:

getEnum(Enum1.class, "A")

edited Oct 15, 2014 at 9:59

answered Oct 14, 2014 at 9:45

EpicPandaForce

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2 Comments

Juh_ Over a year ago

that method seems useful, but I still got the problem of the getEnum signature (I want to wrap the valueOf call into it to add some more code around it.

EpicPandaForce Over a year ago

well based on the valueOf signature, public static <T extends Enum<T>> T valueOf(Class<T> enumType, String name), you would need private static <E extends Enum<E>> E getEnum(Class<E> clazz, String name)

Juh_ · Accepted Answer · 2014-10-14 10:29:34Z

4

For pass classes you should use class

getEnum(Enum1.class,"A")

And then update method signature to

private static Enum getEnum(Class<? extends Enum> E, String name){
    ...
}

edited Oct 14, 2014 at 10:29

Juh_

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answered Oct 14, 2014 at 9:33

WidWing

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4 Comments

Juh_ Over a year ago

It does not correspond to the signature of getEnum which takes a class<Enum>. And if I change that for class<?> then E.getEnumConstants returns object...

WidWing Over a year ago

update method signature to private static Enum getEnum(Class<? extends Enum> E, String name)

Juh_ Over a year ago

alright! And then I can use @Zhuinden Enum.valueOf too :-)

Juh_ Over a year ago

I finally selected Zhuinden answer because it returns the correct Enum type, not just an Enum.

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