Java implements two versions of two way linked list of

Near the Spring Festival, the project is over, waiting to go home for the New Year. The following is the site for you to study the relevant knowledge of the data structure, linked list is often used as a data structure, will now show their implementation as follows, welcome to teach.

The first version of , without the last node, traverses

each time from the root node

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)){
// Remove this element 
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)+"]";
}
/** Node information */
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;
}
} 
}

The second version of has the last node

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){// If the last node is empty then the list is empty 
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)){
// Remove this element 
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)+"]";
}
/** Node information */
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;
}
}
}

Note: neither version takes into account the use of multi-threading.

Above is the site to introduce the Java implementation of two-way linked list (two versions) of the relevant knowledge, I hope to help you.