Sort for Last¶

Rule details


Rule ID	`sort-for-last`
Severity	WARNING — likely performance problem
Confidence	HIGH — structurally proven
Category	Sort abuse
Complexity	O(n log n) → O(n)

Description¶

Detects patterns where a collection is sorted only to retrieve the first or last element. Sorting the entire collection to find a single extreme value is O(n log n) when a linear scan with max() or min() achieves the same result in O(n).

Typical¶

List<Order> sorted = orders.stream()
    .sorted(Comparator.comparing(Order::getTotal).reversed())
    .collect(Collectors.toList());
Order highestValue = sorted.get(0); // Sorted just for this

After¶

Order highestValue = orders.stream()
    .max(Comparator.comparing(Order::getTotal))
    .orElse(null);

Suggestion¶

Use .max(Comparator.comparing(...)) or .min(...) instead of sorting