doubly linked list java implementation code example

Example 1: doubly linked list python

class ListNode:
    def __init__(self, value, prev=None, next=None):
        self.prev = prev
        self.value = value
        self.next = next

class DoublyLinkedList:
    def __init__(self, node=None):
        self.head = node
        self.tail = node
        self.length = 1 if node is not None else 0

    def __len__(self):
        return self.length
   
  	def add_to_head(self, value):
        new_node = ListNode(value, None, None)
        self.length += 1
        if not self.head and not self.tail:
            self.head = new_node
            self.tail = new_node
        else:
            new_node.next = self.head
            self.head.prev = new_node
            self.head = new_node
 
    def remove_from_head(self):
        value = self.head.value
        self.delete(self.head)
        return value

    def add_to_tail(self, value):
        new_node = ListNode(value, None, None)
        self.length += 1
        if not self.tail and not self.head:
            self.tail = new_node
            self.head = new_node
        else:
            new_node.prev = self.tail
            self.tail.next = new_node
            self.tail = new_node
            

    def remove_from_tail(self):
        value = self.tail.value
        self.delete(self.tail)
        return value
            
    def move_to_front(self, node):
        if node is self.head:
            return
        value = node.value
        if node is self.tail:
            self.remove_from_tail()
        else:
            node.delete()
            self.length -= 1
        self.add_to_head(value)
        
    def move_to_end(self, node):
        if node is self.tail:
            return
        value = node.value
        if node is self.head:
            self.remove_from_head()
            self.add_to_tail(value)
        else:
            node.delete()
            self.length -= 1
            self.add_to_tail(value)

    def delete(self, node):
        self.length -= 1
        if not self.head and not self.tail:
            return
        if self.head == self.tail:
            self.head = None
            self.tail = None
        elif self.head == node:
            self.head = node.next
            node.delete()
        elif self.tail == node:
            self.tail = node.prev
            node.delete()
        else:
            node.delete()

    def get_max(self):
        if not self.head:
            return None
        max_val = self.head.value
        current = self.head
        while current:
            if current.value > max_val:
                max_val = current.value
            current = current.next
        return max_val

Example 2: doubly linked list implementation java

class DoublyLinkedList {    
    //A node class for doubly linked list
    class Node{  
        int item;  
        Node previous;  
        Node next;  
   
        public Node(int item) {  
            this.item = item;  
        }  
    }  
    //Initially, heade and tail is set to null
    Node head, tail = null;  
   
    //add a node to the list  
    public void addNode(int item) {  
        //Create a new node  
        Node newNode = new Node(item);  
   
        //if list is empty, head and tail points to newNode  
        if(head == null) {  
            head = tail = newNode;  
            //head's previous will be null  
            head.previous = null;  
            //tail's next will be null  
            tail.next = null;  
        }  
        else {  
            //add newNode to the end of list. tail->next set to newNode  
            tail.next = newNode;  
            //newNode->previous set to tail  
            newNode.previous = tail;  
            //newNode becomes new tail  
            tail = newNode;  
            //tail's next point to null  
            tail.next = null;  
        }  
    }  
   
//print all the nodes of doubly linked list  
    public void printNodes() {  
        //Node current will point to head  
        Node current = head;  
        if(head == null) {  
            System.out.println("Doubly linked list is empty");  
            return;  
        }  
        System.out.println("Nodes of doubly linked list: ");  
        while(current != null) {  
            //Print each node and then go to next.  
            System.out.print(current.item + " ");  
            current = current.next;  
        }  
    }  
}
class Main{
    public static void main(String[] args) {  
        //create a DoublyLinkedList object
        DoublyLinkedList dl_List = new DoublyLinkedList();  
        //Add nodes to the list  
        dl_List.addNode(10);  
        dl_List.addNode(20);  
        dl_List.addNode(30);  
        dl_List.addNode(40);  
        dl_List.addNode(50);  
   
        //print the nodes of DoublyLinkedList  
        dl_List.printNodes();  
    }  
}

Example 3: double linked list java

class doublelinkedlist{  
    Node head;
    Node tail;

    static class Node{
        int data;
        Node previous;
        Node next;

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

    public void addLink(int data) {
        Node node = new Node(data);

        if(head == null) {
            head = tail = node;
            head.previous = null;
        } else {
            tail.next = node;
            node.previous = tail;
            tail = node;
        }
        tail.next = null;
    }
}