Linked List Cycle

Given a linked list, determine if it has a cycle in it.

Whether the fast node can meet the slow node?

    public boolean hasCycle(ListNode head) {
        if (head==null) {
            return false;
        }
        ListNode current = head;
        ListNode fast = head;

        while (fast.next!=null && fast.next.next!=null) {
            current = current.next;
            fast = fast.next.next;
            if (current==fast) {
                return true;
            }
        }

        return false;
    }