public class SinglyLinkedListDemo {

    public static void main(String[] args) {
        // Test with Integer
        SinglyLinkedList<Integer> intList = new SinglyLinkedList<>();
        intList.add(10);
        intList.add(20);
        intList.add(30);

        System.out.println("Integer List:");
        intList.printList();

        // Test with Double
        SinglyLinkedList<Double> doubleList = new SinglyLinkedList<>();
        doubleList.add(1.1);
        doubleList.add(2.2);
        doubleList.add(3.3);

        System.out.println("\nDouble List:");
        doubleList.printList();
    }
}

class SinglyLinkedList<T> {

    private class Node {

        T data;
        Node next;

        Node(T data) {
            this.data = data;
            this.next = null;
        }
    }

    private Node head;

    public SinglyLinkedList() {
        head = null;
    }

    public void add(T data) {
        Node newNode = new Node(data);

        if (head == null) {
            head = newNode;
            return;
        }

        Node current = head;
        while (current.next != null) {
            current = current.next;
        }
        current.next = newNode;
    }

    public void printList() {
        Node current = head;
        while (current != null) {
            System.out.print(current.data + " -> ");
            current = current.next;
        }
        System.out.println("null");
    }
}