cycle

static boolean hasCycle(SinglyLinkedListNode head) {
    SinglyLinkedListNode first = head;
    SinglyLinkedListNode second = head;
    do{
        first = first.next;
        second = second.next;
        second = second != null ? second.next : null;

    }while (first != null  && second != null && first != second);

    if (first == second) return true;
    else return false;

}