public class Problem {

    public static void main(String[] args) {

        List<? extends A> list;

        List<SonA> list2 = new ArrayList<SonA>();

        list = list2;
         list.add(new SonA()  //error

        list2.add(new SonA());

        A a=list.get();

    }

}

class A extends FatherA {

}

class SonA extends A {

}

class FatherA {

}

 public static void main(String[] args) {

         List<? super A> list = new ArrayList<FatherA>();

         // List<? super A> list=new ArrayList<SonA>(); error

         List<FatherA> list2 = new ArrayList<FatherA>();

         list2.add(new FatherA());

         list.add(new SonA());

         // list.add(new FatherA()); error

         Object o = list.get(0);

         FatherA a = (FatherA) o;

     }

 }