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; 
    } 
  }  
} 

/**  
   * 遞歸，在反轉(zhuǎn)當前節(jié)點之前先反轉(zhuǎn)后續(xù)節(jié)點  
   */  
  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;  
  }  
  
  /**  
   * 遍歷，將當前節(jié)點的下一個節(jié)點緩存后更改當前節(jié)點指針  
   *  
   */  
  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;  
    }  
    //將原鏈表的頭節(jié)點的下一個節(jié)點置為null，再將反轉(zhuǎn)后的頭節(jié)點賦給head    
    head.setNextNode(null);  
    head = pre;  
      
    return head;  
  }