generics : getting parameterizedtype classname from a static method?

Question

I have a simple static method :

public static <U> U findStuff(String id) {
    // how can i get the class of type U here ?
    Class classObject = ....;

    return classObject.newInstance();
}

public static void main(String[] args) {
    MyEntity entity = MyClass.<MyEntity>findStuff("abc");
}

I wonder how i can get the class object from the U ?

Currently i have to pass the class around because i dont know the way yet.. so, now im using something like this :

public static <U> U findStuff(Class<U> classObject, String id) {
    return classObject.newInstance();
}

public static void main(String[] args) {
    MyEntity entity = MyClass.findStuff(MyEntity.class, "abc");
}

MByD · Accepted Answer · 2011-05-16 09:30:51Z

4

To get the class of the object, use object.getClass();

By the way, this is a common way to do it that is not related to Generics

answered May 16, 2011 at 9:30

MByD

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2 Comments

Bertie Over a year ago

MByD: Sorry, my bad earlier post. I've updated my post again. Thank you !

MByD Over a year ago

@Albert Kam - I think you can't do it as you describe, but the guy below will probably give you a certain answer in a few minutes :)

Jon Skeet · Accepted Answer · 2011-05-16 09:51:21Z

2

Does

Class<?> classObject = object.getClass();

do enough for you? It's not clear what you need em.find to do.

EDIT: Okay, with the edit, you're running into the problem of type erasure. Basically, you need to pass in the class you're interested in, as you're already doing. See the Java generics FAQ for more information. It's an unfortunate corollary of the way that Java generics are implemented :(

edited May 16, 2011 at 9:51

answered May 16, 2011 at 9:31

Jon Skeet

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2 Comments

Bertie Over a year ago

Jon Skeet: Sorry for the post that doesnt describe my problem. I've updated my post again. Thank you !

Bertie Over a year ago

Jon Skeet: Ah, i dont really understand yet, but will take a look into it. I was thinking something like what is available for parameterized class, like doing the getClass().getGenericSuperClass().getActualTypeArguments. Thank you.

Vincent Mimoun-Prat · Accepted Answer · 2011-05-16 09:30:38Z

1

// because object extends java.lang.Object
Class<?> classObject = object.getClass();

answered May 16, 2011 at 9:30

Vincent Mimoun-Prat

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1 Comment

Bertie Over a year ago

MarvinLabs: Sorry, wrong example in my previous post. I've updated my post again. Thank you !

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