Bug Report for queue

[Sedose]

Bug Report for https://neetcode.io/problems/queue

Describe the bug below and include any steps to reproduce the bug or screenshots if possible.

import java.util.OptionalInt;

public class Deque {
  private static class Node {
    int value;
    Node previous;
    Node next;

    Node(int value) {
      this.value = value;
    }
  }

  private Node head;
  private Node tail;

  public boolean isEmpty() {
    return head == null;
  }

  public void append(int value) {
    Node newTail = new Node(value);
    if (isEmpty()) {
      head = newTail;
      tail = newTail;
      return;
    }
    tail.next = newTail;
    newTail.previous = tail;
    tail = newTail;
  }

  public void appendLeft(int value) {
    Node newHead = new Node(value);
    if (isEmpty()) {
      head = newHead;
      tail = newHead;
      return;
    }
    head.previous = newHead;
    newHead.next = head;
    head = newHead;
  }

  public OptionalInt pop() {
    if (isEmpty()) {
      return OptionalInt.empty();
    }
    int removedValue = tail.value;
    tail = tail.previous;
    if (tail == null) {
      head = null;
    } else {
      tail.next = null;
    }
    return OptionalInt.of(removedValue);
  }

  public OptionalInt popLeft() {
    if (isEmpty()) {
      return OptionalInt.empty();
    }
    int removedValue = head.value;
    head = head.next;
    if (head == null) {
      tail = null;
    } else {
      head.previous = null;
    }
    return OptionalInt.of(removedValue);
  }
}