<@U47K079R7> ``` class A&lt;T&gt; { public &lt;E...

# announcements

[douglarek]

@alband

class A<T> {
  public <E> E get(Class<E> klass, String key) {
    return (E) (new Object()); // just for demo
  }

  public static void main(String[] args) {
    A a = new A<>();
    a.get(List.class,"a");
  }

[alband]

you re instanciating an Object (not a E) and down casting it to E => it should always result a classcastexception if E is not object

[alband]

you have "klass" that should be used to instanciate a E

[alband]

what are you trying to do ?

[douglarek]

ok, I just wrote that for demo

[douglarek]

any resonable codes can be in get method

[Andreas Sinz]

@douglarek what does your code have to do with kotlin?

[alband]

so in your java code you use E and not T... it's what you want ?

[douglarek]

yeah, I want to use <E> not <T> as generic type in get method, although A's generic type is <T>

[douglarek]

@Andreas Sinz it is not about kotlin, I think, sorry for that

[alband]

what is the problem then ?

[alband]

if you want E to be a super type of T you can use E super T.... but yeah this has nothing to do here, on kotlinlang slack

[douglarek]

a.get(List.class,"a"); will return java.lang.Object just not java.util.List when instances A as a raw type

[Andreas Sinz]

give us a real world example on what you are trying to do. i'm still not sure what you are trying to accomplish

[douglarek]

ok

[alband]

+1 with andreas
+ dont forget java has type erasure

[douglarek]

public class Response<T> {
  private Map<String, Object> data = new HashMap<>();

  public <E> E getDataEntryAs(Class<E> type, String key) {

    Object o = data.get(key);
    if (o == null) {
      return null;
    }
    ObjectMapper m = new ObjectMapper();
    return m.convertValue(o, type);
  }
}

[Andreas Sinz]

and what exactly is the problem with this code?

[douglarek]

Response response =  new Response();
    
response.getDataEntryAs(String.class,"");

[douglarek]

just do not know why response.getDataEntryAs(String.class,""); return java.lang.Object

[douglarek]

if

Response<String> response =  new Response<>();
response.getDataEntryAs(String.class,"");

[douglarek]

response.getDataEntryAs(String.class,""); will return java.lang.String

[Andreas Sinz]

are you sure you are using T and E? because Response<String> does not have any impact on your E

[douglarek]

I have other methods will use <T>, but for get it just use <E>

[douglarek]

if response has raw type not generic type, <E> will not work

[Andreas Sinz]

@douglarek the code is working fine here

[douglarek]

ok, just do not know why

[Andreas Sinz]

but i guess your code is different than the one you have posted, because T does not have any impact on E