interface List<A> {
  public void add(A x);
  public Iterator<A> iterator();
}
interface Iterator<A> {
  public A next();
  public boolean hasNext();
}
class LinkedList<A> implements List<A> { ... }
class Test {
  public static void main (String[] args) {

    // byte list
    List<Byte> xs = new LinkedList<Byte>();
    xs.add(new Byte(0)); xs.add(new Byte(1));
    Byte x = xs.iterator().next();

    // string list
    List<String> ys = new LinkedList<String>();
    ys.add("zero"); ys.add("one");
    String y = ys.iterator().next();

    // string list list
    List<List<String>> zss = new LinkedList<List<String>>();
    zss.add(ys);
    String z = zss.iterator().next().iterator().next();

    // string list treated as byte list
    Byte w = ys.iterator().next();  // compile-time error
  }
}

Example 2: Lists, iterators, linked lists, and the test class rewritten in GJ.