LinkedList Revision

public class LinkedList {
    static class Node {
        int data;
        Node next;

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

    static Node head;
    static Node tail;

    public static void addLast(int data){
        // create a node
        Node nn = new Node(data);

        // connect to tail 
        tail.next = nn;

        // update tail
        tail = nn;
    }

    public static void printLL(){
        Node temp = head;

        while(temp!=null){
            System.out.print(temp.data+" ");
            // Node tempKaNext = temp.next;
            // temp = tempKaNext;
            temp = temp.next;
        }
    }

    public static Node getNodeAt(int idx){
        Node temp = head;

        int currentIdx = 0;

        while(currentIdx < idx){
            temp = temp.next;
            currentIdx++;
        }

        return temp;
    }

    public static void addAt(int data, int idx){
        // create a node
        Node currentNode = new Node(data);

        // get idx-1 Node;
        Node prev = getNodeAt(idx-1);

        // getAfterNode
        Node afterNode = prev.next;

        // join prev to currentNode 
        prev.next = currentNode;
        currentNode.next = afterNode;
    }

    public static void main(String[] args) {
        Node n1 = new Node(10);
        Node n2 = new Node(15);
        Node n3 = new Node(20);

        n1.next = n2;
        n2.next = n3;

       head = n1;
       tail = n3;

       addLast(25);

       System.out.println("previous");
       printLL();
       System.out.println();

       addAt(45,3);

       System.out.println("after");
       printLL();
    }
}