package generics.simple;

import java.util.ArrayList;

public class A
{
 public A add(A a) {
 	return null;
 }
}

public class B<T extends A>
{
 ArrayList<T> a;
 
	public T some(T arg) {
        return a.get(0);               // все good - он типа "T"
 	return a.get(0).add(arg);  // error - из "A" "T" не кастится 
        return (T)(a.get(0).add(arg));  // unchecked cast
 }
}

package test;

public class GenTest<T extends A> 
{
 public T get(T arg) {
  T c=arg;
  System.out.println("Before: "+c.getClass().getName());
  c = (T)arg.get(); // Warning: unchecked cast
  System.out.println(" After: "+c.getClass().getName());
  if (c instanceof C)
   ((C)c).print();	 
  return c;
  }
 
 
 
 public static void main(String[] args) {
  GenTest<A> a=new GenTest<>();
  System.out.println("Trying to cast \"C\" from \"B\"");
  B b=(B)a.get(new B());
  System.out.println("\n\nTrying to cast \"B\" from \"C\"");
  a.get(new C());
 }
}