return 0;
          }
        };

    assertEquals(0, (int) iter.next());

    assertThrows(UnsupportedOperationException.class, iter::remove);
  }

  public void testReentrantHasNext() {
    Iterator<Integer> iter =
        new AbstractIterator<Integer>() {
          @Override
          protected Integer computeNext() {
            boolean unused = hasNext();

            return 0;
          }
        };

    assertEquals(0, (int) iter.next());

    assertThrows(UnsupportedOperationException.class, iter::remove);
  }

  public void testReentrantHasNext() {
    Iterator<Integer> iter =
        new AbstractIterator<Integer>() {
          @Override
          protected Integer computeNext() {
            boolean unused = hasNext();