java LinkedList的实例详解

public class LinkedList<E> implements List<E>, Deque<E> {  Node<E> first;  Node<E> last;  int size;   public boolean add(E e) {     final Node<E> l = last;     final Node<E> newNode = new Node<>(l, e, null);     last = newNode;     if (l == null)       first = newNode;     else       l.next = newNode;     size++;     modCount++;     return true;   }   private static class Node<E> {     E item;     Node<E> next;     Node<E> prev;      Node(Node<E> prev, E element, Node<E> next) {       this.item = element;       this.next = next;       this.prev = prev;     }   }  } 

/**     * 递归，在反转当前节点之前先反转后续节点     */    public static Node reverse(Node head) {      if (null == head || null == head.getNextNode()) {        return head;      }      Node reversedHead = reverse(head.getNextNode());      head.getNextNode().setNextNode(head);      head.setNextNode(null);      return reversedHead;    }      /**     * 遍历，将当前节点的下一个节点缓存后更改当前节点指针     *     */    public static Node reverse2(Node head) {      if (null == head) {        return head;      }      Node pre = head;      Node cur = head.getNextNode();      Node next;      while (null != cur) {        next = cur.getNextNode();        cur.setNextNode(pre);        pre = cur;        cur = next;      }      //将原链表的头节点的下一个节点置为null，再将反转后的头节点赋给head        head.setNextNode(null);      head = pre;            return head;    }