Queue Implementation using Linked List

queue.java

public class queue {
    class Node {
        int data;
        Node next;
        Node(int data) {
            this.data = data;
            next = null;
        }
    }

    Node head = null;
    Node tail = null;

    public boolean isEmpty() {
        return head == null && tail == null;
    }

    public void add(int data) {
        Node newNode = new Node(data);
        if(isEmpty()) {
            tail = head = newNode;
        } else {
            tail.next = newNode;
            tail = newNode;
        }
    }

    public int remove() {
        if(isEmpty()) {
            System.out.println("empty queue");
            return -1;
        }
        int front = head.data;
        //single node
        if(head == tail) {
            tail = null;
        }
        head = head.next;
        return front;
    }

    public int peek() {
        if(isEmpty()) {
            System.out.println("empty queue");
            return -1;
        }
        return head.data;
    }

    public static void main(String[] args) {
        queue q = new queue();
        q.add(1);
        q.add(2);
        q.add(3);
        q.add(4);
        q.add(5);

        //here we get the referernce of the current node
        Node current = q.head;
        while(current != null) {
            //current is iterating over each node until it gets last one i.e, null
            System.out.println(current.data); //printing the values
            current = current.next;     //going to the next node
        }
    }
}