Test Time to Complete Codility Java Test - Please give me an estimate

We are trying to assess a codility test for Java, for some of our candidates and whether it is a doable test, given the time limit. For example, would a seasoned Java Developer, of let's say 10 years be able to finish and run and test a small java program for the below question in under 30 minutes? Please, any help on a time estimate would be appreciated.

A pointer is called a linked list if: • it is an empty pointer (it is then called a terminator or an empty list); or • it points to a structure (called a node or the head) that contains a value and a linked list (called the tail). The length of a list is defined as the total number of nodes it contains. In particular, an empty list has length 0. For example, consider the following linked list: A -> B -> C -> D -> This list contains four nodes: A, B, C and D. Node D is the last node and its tail is the terminator. The length of this list is 4. Assume that the following declarations are given: class IntList { public int value; public IntList next; } Write a function: class Solution { public int solution(IntList L); } that, given a non-empty linked list L consisting of N nodes, returns its length. For example, given list L shown in the example above, the function should return 4. Assume that: • N is an integer within the range [1..5,000]; • list L does not have a cycle (each non-empty pointer points to a different structure). In your solution, focus on correctness. The performance of your solution will not be the focus of the assessment.