I’m solving HackerRank “Linked Lists: Detect a Cycle” challenge.

A linked list is said to contain a cycle if any node is visited more than once while traversing the list.

Complete the function provided in the editor below. It has one parameter: a pointer to a Node object named head that points to the head of a linked list. Your function must return a boolean denoting whether or not there is a cycle in the list. If there is a cycle, return true; otherwise, return false.

Note: If the list is empty, head will be null.

/* Detect a cycle in a linked list. Note that the head pointer may be 'null' if the list is empty.  A Node is defined as:      class Node {         int data;         Node next;     } */  boolean hasCycle(Node head) {     HashSet<Node> seen = new HashSet<Node>();      Node current = head;     while (current != null && current.next != null) {         if (seen.contains(current)) {             return true;         }          seen.add(current);         current = current.next;     }      return false; } 

As a beginner Java developer, what can be improved here?