AvlNode() {
      this.elem = null;
      this.elemCount = 1;
    }

    // For discussion of pred() and succ(), see the comment on the pred and succ fields.

    private AvlNode<E> pred() {
      return requireNonNull(pred);
    }

    private AvlNode<E> succ() {
      return requireNonNull(succ);
    }

    int count(Comparator<? super E> comparator, @ParametricNullness E e) {

  private void setSuccessor(int entry, int succ) {
    requireSuccessors()[entry] = succ + 1;
  }

  private void setPredecessor(int entry, int pred) {
    requirePredecessors()[entry] = pred + 1;
  }

  private void setSucceeds(int pred, int succ) {
    if (pred == ENDPOINT) {
      firstEntry = succ;
    } else {
      setSuccessor(pred, succ);
    }

    if (succ == ENDPOINT) {
      lastEntry = pred;

    AvlNode() {
      this.elem = null;
      this.elemCount = 1;
    }

    // For discussion of pred() and succ(), see the comment on the pred and succ fields.

    private AvlNode<E> pred() {
      return requireNonNull(pred);
    }

    private AvlNode<E> succ() {
      return requireNonNull(succ);
    }

    int count(Comparator<? super E> comparator, @ParametricNullness E e) {