lec79_linkedlist_implementation.java

package shreya.java;

public class lec79_linkedlist_implementation {
    public static class Node{   //user defined data type
        int val;
        Node next;
        Node (int val){
            this.val = val;
        }
    }
    public static class queueLL{
        Node head = null;
        Node tail = null;
        int size =0;
        public void add(int x){
            Node temp = new Node(x);
            if(size==0){
                head = tail = temp;
            }
            else{
                tail.next = temp;
                tail = temp;
            }
            size++;
        }
        public int peek(){
            if(size==0){
                System.out.println("queue is empty");
                return -1;
            }
            return head.val;
        }
        public int remove (){
            if (size == 0) {

                System.out.println("Queue is empty");
                return -1;
            }
            int x = head.val;
            head = head.next;
            size--;
            return x;
        }
        public void display(){
            Node temp = head;
            while(temp!= null){
                System.out.print(temp.val+" ");
                temp = temp.next;
            }
            System.out.println();
        }
        public boolean isEmpty(){
            if(size==0)return true;
            else return false;
        }

    }
    public static void main(String[] args) {
       queueLL q1 = new queueLL();
       q1.add(3);
       q1.add(4);
       q1.add(7);
       q1.add(10);
       q1.display();
        System.out.println(q1.peek());
        q1.remove();
        q1.display();


    }
}