[Program]Generic Implementation of custom linked list in java

Data structure is one of the most important in computer science . There are so many data structure are there
if you talk about most important from all the important one is Linked List.

LinkedList is a data structure where there are two block of node,one is data block and second one is for address block , the address block store the address of next node.

Like arrays, Linked List is a linear data structure. Unlike arrays, linked list elements are not stored at contiguous location; the elements are linked using pointers.(source geekforgeeks )

source : wikipedia

Now let see if we want to write our own linked list using generic.

	package javatest;
	/**
	* Interface containing the important methods
	* @author Rajendra
	*
	* @param <T>
	*/
	interface List<T>{
	boolean add(T data);
	boolean remove(T data);
	T get(int index);
	int size();
	void printNodes();
	}
	/**
	* This class implements the list interface and it handles the linked list functionality
	* @author Rajendra
	*
	* @param <T>
	*/
	class LinkedList<T> implements List<T> {
	/**
	* This class is private as this is not exposed outside the linked list class
	* @author Rajendra
	*
	*/
	private class Node{
	private final T data;
	private Node next;
	public Node(T data) {
	super();
	this.data = data;
	}
	public Node getNext() {
	return next;
	}
	public void setNext(Node next) {
	this.next = next;
	}
	public T getData() {
	return data;
	}
	}
	//Represent the first element of the linked list
	private Node head;
	//Represent the last element of the linked list
	private Node tail;
	//Represent the list size
	private int nodeCounter;
	@Override
	public boolean add(T data) {
	boolean addFlag = false;
	//Creating new node with given data
	Node node = new Node(data);
	//Linked list is empty, adding first element
	if(this.head==null) {
	head = node;
	//Head and tail pointing to the same node
	tail=head;
	nodeCounter++;
	addFlag = true;
	}else {
	//Linked list is not empty, adding new element to the list
	tail.setNext(node);
	tail = node;
	nodeCounter++;
	addFlag = true;
	}
	return addFlag;
	}
	@Override
	public boolean remove(T data) {
	boolean removeFlag = false;
	//Checking whether list is empty or not
	if(head==null) {
	throw new IndexOutOfBoundsException("List is empty");
	}
	//Deleting head element
	if(head.getData().equals(data)) {
	Node temp = head;
	head = temp.getNext();
	temp = null;
	this.nodeCounter--;
	removeFlag = true;
	}else {
	Node temp = head.getNext();
	Node prev = head;
	// Iterating over the list
	while(temp!=null) {
	// Checking the data for node deletion
	if(temp.getData().equals(data)) {
	prev.setNext(temp.getNext());
	temp = null;
	this.nodeCounter--;
	removeFlag = true;
	break;
	}
	prev = temp;
	temp = temp.getNext();
	}
	}
	return removeFlag;
	}
	@Override
	public void printNodes() {
	Node temp = head;
	while(temp!=null) {
	System.out.print(temp.getData()+" ");
	temp= temp.getNext();
	}
	System.out.println();
	}
	@Override
	public int size() {
	return this.nodeCounter;
	}
	@Override
	public T get(int index) {
	T data = null;
	Node temp = head;
	int cntr = 0;
	if(head==null)
	throw new IndexOutOfBoundsException("List is empty");
	if(index>=this.nodeCounter)
	throw new IndexOutOfBoundsException("Index greater than list size");
	//If given index is of head node then return the data
	if(index==cntr)
	data = head.getData();
	//If given index is of tail node then return data
	else if(index==(nodeCounter-1))
	data = tail.getData();
	else {
	//Checking the given index with the node index
	while(temp!=null) {
	if(cntr==index) {
	data = temp.getData();
	break;
	}
	temp= temp.getNext();
	cntr++;
	}
	}
	return data;
	}
	}
	/**
	* This the test class for linked list implementation
	* @author Rajendra
	*
	*/
	public class OwnLinkedListTest {
	public static void main(String[] args) {
	List<Integer> l1 = new LinkedList<Integer>();
	l1.add(1);
	l1.add(2);
	l1.add(3);
	l1.add(4);
	l1.add(5);
	l1.add(6);
	System.out.println("Get 0th element : "+l1.get(0));
	System.out.println("Get inbetween index element : "+l1.get(3));
	System.out.println("Get last element : "+l1.get(5));
	System.out.println("Int list size : "+l1.size());
	l1.printNodes();
	System.out.println("Remove head : "+l1.remove(1));
	System.out.println("Int list size : "+l1.size());
	l1.printNodes();
	System.out.println("Remove tail : "+l1.remove(6));
	System.out.println("Int list size : "+l1.size());
	l1.printNodes();
	System.out.println("Remove inbetween node : "+l1.remove(3));
	System.out.println("Int list size : "+l1.size());
	l1.printNodes();
	System.out.println("Get element index greater than size : "+l1.get(5));
	}
	}

view raw OwnLinkedList.java hosted with ❤ by GitHub

If you have any problem you can leave us a comment ,
This program is contributed by Rajendra Tighage

Thanks for Reading
Noeik