Java Program to Implement Doubly Linked List

	/*
	* Java Program to Implement Doubly Linked List
	*/
	import java.util.Scanner;
	/* Class Node */
	class Node {
	protected int data;
	protected Node next, prev;
	/* Constructor */
	public Node() {
	next = null;
	prev = null;
	data = 0;
	}
	/* Constructor */
	public Node(int d, Node n, Node p) {
	data = d;
	next = n;
	prev = p;
	}
	/* Function to set link to next node */
	public void setLinkNext(Node n) {
	next = n;
	}
	/* Function to set link to previous node */
	public void setLinkPrev(Node p) {
	prev = p;
	}
	/* Funtion to get link to next node */
	public Node getLinkNext() {
	return next;
	}
	/* Function to get link to previous node */
	public Node getLinkPrev() {
	return prev;
	}
	/* Function to set data to node */
	public void setData(int d) {
	data = d;
	}
	/* Function to get data from node */
	public int getData() {
	return data;
	}
	}
	/* Class linkedList */
	class linkedList {
	protected Node start;
	protected Node end;
	public int size;
	/* Constructor */
	public linkedList() {
	start = null;
	end = null;
	size = 0;
	}
	/* Function to check if list is empty */
	public boolean isEmpty() {
	return start == null;
	}
	/* Function to get size of list */
	public int getSize() {
	return size;
	}
	/* Function to insert element at begining */
	public void insertAtStart(int val) {
	Node nptr = new Node(val, null, null);
	if (start == null) {
	start = nptr;
	end = start;
	} else {
	start.setLinkPrev(nptr);
	nptr.setLinkNext(start);
	start = nptr;
	}
	size++;
	}
	/* Function to insert element at end */
	public void insertAtEnd(int val)
	{
	Node nptr = new Node(val, null, null);
	if (start == null) {
	start = nptr;
	end = start;
	} else {
	nptr.setLinkPrev(end);
	end.setLinkNext(nptr);
	end = nptr;
	}
	size++;
	}
	/* Function to insert element at position */
	public void insertAtPos(int val, int pos) {
	Node nptr = new Node(val, null, null);
	if (pos == 1) {
	insertAtStart(val);
	return;
	}
	Node ptr = start;
	for (int i = 2; i <= size; i++) {
	if (i == pos) {
	Node tmp = ptr.getLinkNext();
	ptr.setLinkNext(nptr);
	nptr.setLinkPrev(ptr);
	nptr.setLinkNext(tmp);
	tmp.setLinkPrev(nptr);
	}
	ptr = ptr.getLinkNext();
	}
	size++;
	}
	/* Function to delete node at position */
	public void deleteAtPos(int pos) {
	if (pos == 1) {
	if (size == 1) {
	start = null;
	end = null;
	size = 0;
	return;
	}
	start = start.getLinkNext();
	start.setLinkPrev(null);
	size--;
	return;
	}
	if (pos == size) {
	end = end.getLinkPrev();
	end.setLinkNext(null);
	size--;
	}
	Node ptr = start.getLinkNext();
	for (int i = 2; i <= size; i++) {
	if (i == pos) {
	Node p = ptr.getLinkPrev();
	Node n = ptr.getLinkNext();
	p.setLinkNext(n);
	n.setLinkPrev(p);
	size--;
	return;
	}
	ptr = ptr.getLinkNext();
	}
	}
	/* Function to display status of list */
	public void display() {
	System.out.print("\nDoubly Linked List = ");
	if (size == 0) {
	System.out.print("empty\n");
	return;
	}
	if (start.getLinkNext() == null) {
	System.out.println(start.getData());
	return;
	}
	Node ptr = start;
	System.out.print(start.getData() + " <-> ");
	ptr = start.getLinkNext();
	while (ptr.getLinkNext() != null) {
	System.out.print(ptr.getData() + " <-> ");
	ptr = ptr.getLinkNext();
	}
	System.out.print(ptr.getData() + "\n");
	}
	}
	/* Class DoublyLinkedList */
	public class DoublyLinkedList {
	public static void main(String[] args) {
	Scanner scan = new Scanner(System.in);
	/* Creating object of linkedList */
	linkedList list = new linkedList();
	System.out.println("Doubly Linked List Test\n");
	char ch;
	/* Perform list operations */
	do {
	System.out.println("\nDoubly Linked List Operations\n");
	System.out.println("1. insert at begining");
	System.out.println("2. insert at end");
	System.out.println("3. insert at position");
	System.out.println("4. delete at position");
	System.out.println("5. check empty");
	System.out.println("6. get size");
	int choice = scan.nextInt();
	switch (choice) {
	case 1:
	System.out.println("Enter integer element to insert");
	list.insertAtStart(scan.nextInt());
	break;
	case 2:
	System.out.println("Enter integer element to insert");
	list.insertAtEnd(scan.nextInt());
	break;
	case 3:
	System.out.println("Enter integer element to insert");
	int num = scan.nextInt();
	System.out.println("Enter position");
	int pos = scan.nextInt();
	if (pos < 1 || pos > list.getSize())
	System.out.println("Invalid position\n");
	else
	list.insertAtPos(num, pos);
	break;
	case 4:
	System.out.println("Enter position");
	int p = scan.nextInt();
	if (p < 1 || p > list.getSize())
	System.out.println("Invalid position\n");
	else
	list.deleteAtPos(p);
	break;
	case 5:
	System.out.println("Empty status = " + list.isEmpty());
	break;
	case 6:
	System.out.println("Size = " + list.getSize() + " \n");
	break;
	default:
	System.out.println("Wrong Entry \n ");
	break;
	}
	/* Display List */
	list.display();
	System.out.println("\nDo you want to continue (Type y or n) \n");
	ch = scan.next().charAt(0);
	} while (ch == 'Y' || ch == 'y');
	}
	}

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