Java generics incompatible type

Question

I have this method (using generics) :

public class ExtA<T>Ex<T> extends ArrayList
{    
    public<T> ExtA<T>Ex<T> filt(Function<T, Boolean> a...)
    {
  //code
    }
}

giving me an "incompatible types error".

possible duplicate of [Java Generics and generic types](http://stackoverflow.com/questions/20908742/java-generics-and-generic-types) — Elliott Frisch, Jan 03 '14 at 17:19
Because I had another problem, still left the question relavant to the answer — user3126119, Jan 03 '14 at 18:48

score 5 · Accepted Answer · answered Jan 03 '14 at 17:18

5

Remove the leading <T> from your filt method declaration. It's shadowing the generic T type applied to the class.

answered Jan 03 '14 at 17:18

@user3126119 That should be fine, since it appears that you're adding behavior (the filtering) without changing the data structure of the class. – chrylis -cautiouslyoptimistic- Jan 03 '14 at 17:22
Always use the genericized type if available. In this case, the raw type should give you compiler warnings; pay attention to them. – chrylis -cautiouslyoptimistic- Jan 03 '14 at 18:10
@user3126119 Don't. Use `ExtA eal3 = al.filt();`. – chrylis -cautiouslyoptimistic- Jan 03 '14 at 18:49
then how should I call it? – user3126119 Jan 03 '14 at 18:50
@user3126119 Like I just posted in that comment. – chrylis -cautiouslyoptimistic- Jan 03 '14 at 19:57
I tried but I need to call it from the main methods and it is telling me "cannot find symbol- class T" – user3126119 Jan 03 '14 at 20:50
@user3126119 You have to use the same class parameter you used for `al`. – chrylis -cautiouslyoptimistic- Jan 03 '14 at 20:52

1 Answers1