Static Generic types

[O. Ziggy]

Why is the following not allowed

public class Gen<T> {
  public static T foo; // compiler error
}

Can i see an example as to why this is not a good idea.

Thanks

[Paul Clapham]

Consider

Gen<String> first = new Gen<String>();
Gen<Integer>second = new Gen<Integer>();

Now what is the type of Gen.foo?

[Dan Drillich]

The compiler error is -

Cannot make a static reference to the non-static type T

Regards,
Dan

[O. Ziggy]

Ok got that. What about when the type parameter is on the method:

    public class Gen {  
      public static <T> T foo;
    }  

The above is allowed. Does this not cause the same issue? i.e. what type will foo() return?

[Paul Clapham]

It will return whatever type is specified (or inferred) on the method call.

[O. Ziggy]

Can you provide an example of how that method would be used. (I dont really get it).

Thanks

[Tomasz Sochanski]

read this thread https://coderanch.com/t/562466/java-programmer-SCJP/certification/Genrics-ReturnType

[O. Ziggy]

Thank you all.