Linked list in Java

class ListNode {
    int val;
    ListNode next;
    ListNode(int val) { this.val = val; }
}

ListNode reverseList(ListNode head) {
    ListNode prev = null;
    ListNode curr = head;

    while (curr != null) {
        ListNode next = curr.next;
        curr.next = prev;
        prev = curr;
        curr = next;
    }
    return prev;
}