static <T> void compactNulls(ArrayList<T> list) {
    list.removeIf(Objects::isNull);
  }
@Test
  public void shouldCompactNulls2() {
    ArrayList<Integer> listBad = (ArrayList) Lists.newArrayList(1);
    MutableFSTImpl.compactNulls(listBad);
    assertEquals(Lists.newArrayList(1), listBad);
  }