public void removeAllFields() {
    FastSparseSet<Integer>[] arr = elements[2];
    int[] arrnext = next[2];

    for (int i = arr.length - 1; i >= 0; i--) {
      FastSparseSet<Integer> val = arr[i];
      if (val != null) {
        arr[i] = null;
        size--;
      }
      arrnext[i] = 0;
    }
  }
public void removeAllFields()