Java - Generic function to parse enums from strings

Question

I need to create a generic function that will parse enums from strings, but i'm not sure about the syntax to use.

This doesn't work, but it illustrate what i want to do :

public <E extends Enum<E>> getEnum( some params, <E extends Enum<E>> defaultVal )
{
    // Some stuff

    return E.valueOf( enumAsString );
}

What is wrong in my syntax please ? Thank you :)

EDIT : Also how do i use this ? In C++ i would do SomeEnum e = getEnum<SomeEnum>( ... );

EDIT :

Let

enum EnumA
{
    A_A, A_B, A_C
};

enum EnumB
{
    B_A, B_B, B_C
};

I would like to do :

String enumAsStr = "A_B";
EnumA ea = getEnum< EnumA >( enumAsStr, "A_A" );

enumAsStr = "B_C";
EnumB eb = getEnum< EnumB >( enumAsStr, "B_A" );

Am I getting this right: You want to find an Enum by one of its elements given as String? — Fildor
– Fildor, Commented Aug 25, 2014 at 14:02
Yes the enum as it appears in the source code is stored in the given string, and i also pass a default value in case the parsing fails. — Virus721
– Virus721, Commented Aug 25, 2014 at 14:02
Yes but that's very vague. I know how to get the value of an enum from it's name, i just don't know the Java syntax to use for a function returning a generic type that can only be an enum. — Virus721
– Virus721, Commented Aug 25, 2014 at 14:05

Edwin Dalorzo · Accepted Answer · 2014-08-25 14:04:47Z

5

You could do something like

public <E extends Enum<E>> E getEnum( String text, Class<E> klass){
   return Enum.valueOf(klass, text );
}

So, for instance if there is an enum Letter

public enum Letter { A, B, C}

You could use it like this:

Letter someLetter = getEnum("A", Letter.class);
System.out.println(someLetter); //A

answered Aug 25, 2014 at 14:04

Edwin Dalorzo

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3 Comments

Virus721 Over a year ago

Thanks for your answer. That looks to be what i'm looking for, but in my example the last parameter was used for a default enum to return in case the parsing fails. In my example "E" reprensts my enum type right ? Can't i do E.valueOf(someString) ?

Virus721 Over a year ago

Couldn't i do instead : public <E extends Enum<E>> E getEnum( String text ) { Class< E > klass; return Enum.valueOf( klass.class, text ); }

NoDataFound Over a year ago

You can't. Enum.valueOf need a class of some enumerate to do its works. And beside, you don't initialize it, and if you could, you would have problems with type erasure.

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