第一个版本，没有最后一个节点，每次从根节点开始遍历

public class  LinkedList<E> {             private Node head;             public LinkedList() {      }             public E getFirst(){          if(head==null){              return null;          }          return head.value;      }             public LinkedList<E> addFirst(E e){          head.pre=new Node(e, null, head);          head=head.pre;          return this;      }             public LinkedList<E> addNode(E e){          Node lst=head;          if(lst==null){              this.head=new Node(e, null, null);              return this;          }else{              while(true){                  if(lst.next==null){                      break;                  }else{                      lst=lst.next;                  }              }              lst.next=new Node(e, lst, null);              return this;          }      }             public LinkedList<E> remove(E e){          Node lst=head;          if(lst==null){              throw new NullPointerException("the LinkedList is empty.");          }else{              while(true){                  if(e.equals(lst.value)){                      //移除这个元素                      if(lst.pre!=null){                          lst.pre.next=lst.next;                      }                      if(lst.next!=null){                          lst.next.pre=lst.pre;                      }                      lst=null;                      break;                  }                  lst=lst.next;              }              return this;          }      }                    @Override      public String toString() {          StringBuffer buff=new StringBuffer("[");          Node lst=this.head;          while(lst!=null){              buff.append(lst.value+",");              lst=lst.next;          }          return buff.substring(0, buff.length()-1)+"]";      }             /**节点信息*/      private class Node{          public Node pre;          public E value;          public Node next;                     public Node(E value,Node pre,Node next) {              this.value=value;              this.pre=pre;              this.next=next;          }      }         }

第二个版本，有了最后一个节点

public class  LinkedList<E> {            private Node head;      private Node last;            public LinkedList() {      }            public E getFirst(){          if(head==null){              return null;          }          return head.value;      }      public E getLast(){          if(last==null){              return null;          }          return last.value;      }            public LinkedList<E> addFirst(E e){          head.pre=new Node(e, null, head);          head=head.pre;          return this;      }            public LinkedList<E> addNode(E e){          Node lst=last;          if(lst==null){//如果最后一个节点是空的则这个链表就是空的              this.last=new Node(e, null, null);              this.head=this.last;              return this;          }else{              while(true){                  if(lst.next==null){//                      break;                  }else{                      lst=lst.next;                  }              }              lst.next=new Node(e, lst, null);              last=lst.next;              return this;          }      }            public LinkedList<E> remove(E e){          Node lst=head;          if(lst==null){              throw new NullPointerException("the LinkedList is empty.");          }else{              while(true){                  if(e.equals(lst.value)){                      //移除这个元素                      if(lst.pre!=null){                          lst.pre.next=lst.next;                      }                      if(lst.next!=null){                          lst.next.pre=lst.pre;                      }                      lst=null;                      break;                  }                  lst=lst.next;              }              return this;          }      }                  @Override      public String toString() {          StringBuffer buff=new StringBuffer("[");          Node lst=this.head;          while(lst!=null){              buff.append(lst.value+",");              lst=lst.next;          }          return buff.substring(0, buff.length()-1)+"]";      }            /**节点信息*/      private class Node{          public Node pre;          public E value;          public Node next;                    public Node(E value,Node pre,Node next) {              this.value=value;              this.pre=pre;              this.next=next;          }      }        }

注：以上两个版本都没有考虑在多线程下使用的情况。