1Z0-829 Working with Arrays and Collections Practice Question

A Java 17 application uses a HashMap<Integer, List<String>> to group error messages by error code. The map may contain up to 5000 error codes, and each list may contain up to 1000 messages. The application frequently retrieves the list for a given error code and iterates over it. The lists are rarely modified after initial population. The current performance is acceptable, but the team wants to reduce memory footprint. The developer suggests replacing the inner List<String> with an array (String[]), but then iteration would require conversion. Another developer suggests using a TreeMap instead of HashMap to save memory because TreeMap uses less memory per entry? Actually TreeMap has more overhead. Actually HashMap typically has lower overhead than TreeMap. The correct approach: Since lists are rarely modified, consider using List.of to create immutable lists that can be shared? Or use ArrayList with initial capacity to reduce resizing. But the stem says 'reduce memory footprint'. Option C: Use ArrayList with initial capacity to reduce internal array resizing overhead. Option A: Use TreeMap - wrong because TreeMap uses more memory per entry due to tree nodes. Option B: Use array of arrays - not type-safe. Option D: Use LinkedList - higher memory overhead per element. So best is to use ArrayList with proper sizing to minimize wasted space.