Method push

13_Stacks/StackLL.java:15–24

(int data)

    static class Stack {
        public static Node head = null;
        public static void push(int data) {
            Node newNode = new Node(data);

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

        public static boolean isEmpty() {
            return head == null;