error

Functor.java:8: error: unexpected type
  public <B> F<B> fmap(Function<A, B> f);
             ^
  required: class
  found:    type parameter F
  where F is a type-variable:
    F extends Object declared in interface Functor
1 error

Functor.java

interface Function<A, B> {
  public B call(A arg);
}

interface Functor<F, A> {
  public <B> F<B> fmap(Function<A, B> f);
}

class List<A> implements Functor<List, A> {
  private ArrayList<A> lst = new ArrayList<A>();

  public <B> List<B> fmap(Function<A, B> f) {
    List<B> out = new List<B>();
    for (A tmp : this.lst) {
      out.lst.add(f.call(tmp));
    }
    return out;
  }
} 

// List<Integer> foo = new List<Integer>();
// foo.lst.add(1);
// Function<Integer, String> toString = new Function<Integer, String>() {
//   public String call(A arg) { return arg.toString(); }
// }
// List<String> bar = foo.fmap(toString);