public class List {

    Node head;

    public List() {
        head = null;
    }

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

    public void insert(int data) {
        Node node = new Node(data, head);
        head = node;
    }

    public void modify() {
        Node current = head;
        while(current.next != null) {
            int min = Math.min(current.getData(), current.next.getData());
            int max = Math.max(current.getData(), current.next.getData());
            int newData = Math.abs(max - min);
            Node newNode = new Node(newData, null);
            newNode.next = current.next;
            current.next = newNode;
            current = newNode.next;
            System.out.println(this);
        }
    }

    @Override
    public String toString() {
        String output = "{";
        Node current = head;
        while(current != null) {
            output += " " + current.getData();
            output += (current.next == null) ? "" : ", ";
            current = current.next;
        }
        output += "}\n";
        return output;
    }

    public static void main(String[] args) {
        List list = new List();
        list.insert(8);
        list.insert(3);
        list.insert(5);
        list.insert(2);
        list.insert(4);
        System.out.println(list);
        list.modify();
        System.out.println(list);
    }
}