382. Linked List Random Node 

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class Solution {
    private final ListNode head;

    public Solution(ListNode head) {
        this.head = head;
    }

    public int getRandom() {
        int bound = 1, res = 0;

        ListNode node = head;
        while (node != null) {
            if (ThreadLocalRandom.current().nextInt(bound) == 0) {
                res = node.val;
            }
            bound++;
            node = node.next;
        }

        return res;
    }
}

References

382. Linked List Random Node