Java program to delete a new node from the end of the doubly linked list

by Online Tutorials Library July 22, 2022

Java program to delete a new node from the end of the doubly linked list

In this program, we will create a doubly linked list and delete a node from the end of the list. If the list is empty, print the message “List is empty”. If the list is not empty, tail’s previous node will become the new tail of the list thus, deleting the last node from the list.

In above example, node new was the tail of the list. Make tail’s previous node that is, node 4 as the tail of the list. Node 4’s next will point to null.

Algorithm

Define a Node class which represents a node in the list. It will have three properties: data, previous which will point to the previous node and next which will point to the next node.
Define another class for creating the doubly linked list, and it has two nodes: head and tail. Initially, head and tail will point to null.
deleteFromEnd() will delete a node from the end of the list:
- It first checks whether the head is null (empty list) then, it will return from the function as there is no node present in the list.
- If the list is not empty, it will check whether the list has only one node.
- If the list has only one node, it will set both head and tail to null.
- If the list has more than one node then, tail’s previous node will become the new tail of the list.
- This new tail will point to null thus, delete the last node of the list.

a. display() will show all the nodes present in the list.

Define a new node ‘current’ that will point to the head.
Print current.data till current points to null.
Current will point to the next node in the list in each iteration.

Program:

  public class DeleteEnd {        //Represent a node of the doubly linked list        class Node{          int data;          Node previous;          Node next;            public Node(int data) {              this.data = data;          }      }        //Represent the head and tail of the doubly linked list      Node head, tail = null;        //addNode() will add a node to the list      public void addNode(int data) {          //Create a new node          Node newNode = new Node(data);            //If list is empty          if(head == null) {              //Both head and tail will point to newNode              head = tail = newNode;              //head’s previous will point to null              head.previous = null;              //tail’s next will point to null, as it is the last node of the list              tail.next = null;          }          else {              //newNode will be added after tail such that tail’s next will point to newNode              tail.next = newNode;              //newNode’s previous will point to tail              newNode.previous = tail;              //newNode will become new tail              tail = newNode;              //As it is last node, tail’s next will point to null              tail.next = null;          }      }        //deleteFromEnd() will delete a node from the end of the list      public void deleteFromEnd() {          //Checks whether list is empty          if(head == null) {              return;          }          else {              //Checks whether the list contains only one node              if(head != tail) {                  //Previous node to the tail will become new tail                  tail = tail.previous;                  //Node next to current tail will be made null                  tail.next = null;              }              //If the list contains only one element              //Then it will remove node and now both head and tail will point to null              else {                  head = tail = null;              }          }      }        //display() will print out the nodes of the list      public void display() {          //Node current will point to head          Node current = head;          if(head == null) {              System.out.println(“List is empty”);              return;          }          while(current != null) {              //Prints each node by incrementing the pointer.                System.out.print(current.data + ” “);              current = current.next;          }          System.out.println();      }        public static void main(String[] args) {            DeleteEnd dList = new DeleteEnd();          //Add nodes to the list          dList.addNode(1);          dList.addNode(2);          dList.addNode(3);          dList.addNode(4);          dList.addNode(5);            //Printing original list          System.out.println(“Original List: “);          dList.display();          while(dList.head != null) {              dList.deleteFromEnd();              //Printing updated list              System.out.println(“Updated List: “);              dList.display();          }      }  }  

Output:

Original List:   1 2 3 4 5   Updated List:   1 2 3 4   Updated List:   1 2 3   Updated List:   1 2   Updated List:   1   Updated List:   List is empty

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