Remove First In Linkedlist

 

import java.io.BufferedReader;
import java.io.InputStreamReader;
/*
addLast 10
addLast 20
addLast 30
display
removeFirst
size
addLast 40
addLast 50
removeFirst
display
size
removeFirst
removeFirst
removeFirst
removeFirst
quit
 */
public class Remove_FIrst_In_LinkedList {
    public static class Node {
        int data;
        Node next;
    }

    public static class LinkedList {
        Node head;
        Node tail;
        int size;

        void addLast(int val) {
            Node temp = new Node();
            temp.data = val;
            temp.next = null;

            if (size == 0) {
                head = tail = temp;
            } else {
                tail.next = temp;
                tail = temp;
            }

            size++;
        }

        public int size() {
            return size;
        }

        public void display() {
            for (Node temp = head; temp != null; temp = temp.next) {
                System.out.print(temp.data + " ");
            }
            System.out.println();
        }

        // write your code here
        public void removeFirst() {
            if (head != null) {
                head = head.next;
                size--;
            } else {
                System.out.println("List is empty");
            }
        }
    }

    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        LinkedList list = new LinkedList();

        String str = br.readLine();
        while (str.equals("quit") == false) {
            if (str.startsWith("addLast")) {
                int val = Integer.parseInt(str.split(" ")[1]);
                list.addLast(val);
            } else if (str.startsWith("size")) {
                System.out.println(list.size());
            } else if (str.startsWith("display")) {
                list.display();
            } else if (str.startsWith("removeFirst")) {
                list.removeFirst();
            }
            str = br.readLine();
        }
    }
}