How to cast a String value to an Enum value by Class?

Question

I have the following class:

public class EnumContainer{

    private Class<?> enumClass;
    //GET, SET

    public EnumContainer(Class<?> clazz){
        this.enumClass = clazz;
    }

    public boolean tryCast(String value){
        //Here I should try to cast the String to the Enum by enumClass field

        //return true if cast was successfull
        //false otherwise
    }
}

Is it even possible in Java to perform such casting?

@VinceEmigh Because I'm using hibernate and in order to simplify some mappings I need to use `@Type` annotation which reffers to the type that have to containt the Class> field. From the web page I can only grab a String value. — user3663882, Apr 22 '15 at 08:30
@fge What object should I perform `method.invoke(obj, args)` call on? — user3663882, Apr 22 '15 at 08:39
You never stated you didn't have access to the actual enum.. Maybe be a little more clear in your question next time? — Vince, Apr 22 '15 at 08:42
@VinceEmigh Since I provide the Class> type of that enum it should be clear that I don't have that access. — user3663882, Apr 22 '15 at 08:43
It's obviously not clear. Look at the 4 upvotes on the first comment. — Vince, Apr 22 '15 at 08:44
@VinceEmigh You can do `valueOf` with just a Class, you just call the static method on `Enum`. — Radiodef, Apr 22 '15 at 08:45
@Radiodef BTW don't you why the `enumClass.getMethod("valueOf")` method throws `NoSuchMethodException` although `enumClass.getMethods()` returns the array of `Methods` containing an instance with name `valueOf`? — user3663882, Apr 22 '15 at 08:53
@user3663882 You need something like `enumClass.getMethod("valueOf", enumClass)` because it takes a parameter. I don't really see a reason to use reflection here, though. — Radiodef, Apr 22 '15 at 08:55
@Radiodef Doesn't work as well. The same excpetion is thrown. — user3663882, Apr 22 '15 at 08:56
You'd need `enumClass.getMethod("valueOf", String.class)`, my mistake. Example: [http://ideone.com/dwcbks](http://ideone.com/dwcbks). — Radiodef, Apr 22 '15 at 08:58

Radiodef · Accepted Answer · 2015-04-22T09:02:43.763

It's actually kind of a pain because of the way Enum is declared. You wouldn't be able to call valueOf with a Class<?> (nor e.g. a Class<? extends Enum<?>>). The only way to do it without unchecked casting is to go through getEnumConstants:

public boolean tryCast(String value){
    for(Object o : enumClass.getEnumConstants()) {
        Enum<?> e = (Enum<?>) o;
        if(e.name().equals(value))
            return true;
    }
    return false;
}

If you don't care about the unchecked cast you can do:

try {
    Enum.valueOf( (Class) enumClass, value );
    return true;
} catch(IllegalArgumentException e) {
    return false;
}

But, you know, some people will grumble because it's a raw type. getEnumConstants is probably better anyways since then you don't use exceptions for this kind of thing.

In addition, since you have a Class<?> you might want to perform a check like

if( !Enum.class.isAssignableFrom(enumClass) )
    return false;

or throw an exception in the constructor.

Well, unchecked casting is always not a very good idea... And sincee I don't know how exactly it works internally I would prefer to not using your last aaproach. — user3663882, Apr 22 '15 at 08:48
@user3663882 Then don't. I'm one of the people who grumbles so it's fine with me if you don't. ; ) — Radiodef, Apr 22 '15 at 08:48

How to cast a String value to an Enum value by Class?

1 Answers1