Who says java does not supports pointers, See, how to implement Single Linked List in Java

This very nice code is implemented by -

Vasu Gupta / IT / Maharaja Agrasen Institute of Technology

# in this code a single linked list is been implement , which is a linear data structure, very very important and useful data structure in software engineering

# save this class inside Node.java file # 

import java.util.Scanner;

// Create a node class for creating new nodes in linked list

public class Node{

private int data ;  // data of that node

private Node next ; // node data of next linked node

public Node() { // initialize new node

data = 0 ;

next = null ;

}

// Input data in new node

public Node(int d , Node n) {

data = d ;

next = n ;

}

// set link to the next node

public void setLink(Node link) {

next = link ;

}

// Get link to the next node

public Node getLink() {

return next ;

}

// Get data of the current node

public int getData() {

return data ;

}

}

# save this class inside LinkList.java file # 

// class for creating linked list

public class LinkList {

private Node start ;

private Node end ;

public int size ;

// Initialize all the variables

public LinkList() {

start = null ;

end = null ;

size = 0 ;

}

// Adding nodes at starting of the linked list

public void addAtStart(int data) {

Node node = new Node(data , null);  // Create object of Node class

size++ ; // Increment size of linked list

if(start == null) {

start = node ; // make node the starting node

end = start ;  // make node the ending node

}else {

node.setLink(start); // Attach new node before start

start = node ;  // make the new node as start

}

}

// Adding node at end of the linked list

public void addAtEnd(int data) {

Node node = new Node(data , null);

size++ ;

if(start == null) {

start = node ;

end = start ;

}else {

end.setLink(node); // Attach new node after end

end = node ;       // make the new node as end

}

}

// Adding node at the middle of the linked list

public void addAtMiddle(int data , int pos) {

Node node = new Node(data , null);

size++ ;

Node preptr = start ;

Node ptr = start ;

ptr = ptr.getLink();

int count = 1 ;

while(count != pos) {

preptr = preptr.getLink();

ptr = ptr.getLink();

count++ ;

}

preptr.setLink(node);

node.setLink(ptr);

}

// Adding node after a certain data of the linked list

public void addAfterData(int data , int refData) {

Node node = new Node(data , null);

size++ ;

Node preptr = start ;

Node ptr = start ;

ptr = ptr.getLink();

while(preptr.getData() != refData) {

preptr = preptr.getLink();

ptr = ptr.getLink();

}

preptr.setLink(node);

node.setLink(ptr);

}

// Deleting node in linked list

public void deleteNode(int refData) {

Node preptr = start ;

Node ptr = start ;

ptr = ptr.getLink();

while(ptr.getData() != refData) {

preptr = preptr.getLink();

ptr = ptr.getLink();

}

preptr.setLink(ptr.getLink());

ptr = null ;

size-- ; // Reduce size of linked list

}

// Traversing through linked list and showing data

public void showData() {

if(start == null) {

System.out.println("No data");

}else {

Node ptr = start ;

while(ptr.getLink() != null) {

System.out.print(ptr.getData() + "--->");

ptr = ptr.getLink();

}

System.out.print(ptr.getData());

}

}

}

# save this class inside SingleLinkedList.java file #

# this class is haiving main method # 

public class SingleLinkedList {

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

int data = 0  ;

LinkList ll = new LinkList();

System.out.println("Choose : \n1. Insert at Start \n2. Insert At End");

switch (sc.nextInt()) {

case 1:

// Get data from user again and again and add them to linked list

do {

System.out.print("Enter the data : ");

data = sc.nextInt();

ll.addAtStart(data);

System.out.print("Do you want to add more (y/n) : ");

}while(sc.next().equals("y"));

ll.showData();  // show data of linked list

break;

case 2:

do {

System.out.print("Enter the data : ");

data = sc.nextInt();

ll.addAtEnd(data);

System.out.print("Do you want to add more (y/n) : ");

}while(sc.next().equals("y"));

ll.showData();

break;

default:

break;

}

System.out.println("\nChoose : \n1. Insert At Middle \n2. Insert After A Data \n3. Delete A Node");

switch (sc.nextInt()) {

case 1:

System.out.print("Enter the data : ");

data = sc.nextInt();

int pos = 0 ;

// Calculating middle position

if(ll.size%2 == 0) {

pos = ll.size/2 ;

}else {

pos = (ll.size - 1)/2 ;

}

ll.addAtMiddle(data , pos);

ll.showData();

break;

case 2:

System.out.print("Enter the data : ");

data = sc.nextInt();

System.out.print("Enter the data after which you want to add new data : ");

ll.addAfterData(data , sc.nextInt());

ll.showData();

break;

case 3:

System.out.print("Enter the data to be deleted : ");

data = sc.nextInt();

ll.deleteNode(data); // Delete node

ll.showData();

break;

default:

break;

}

}

}