Repeated Linear Scan

Rule details

Rule ID	repeated-linear-scan
Severity	WARNING — likely performance problem
Confidence	LOW — heuristic-heavy, may produce false positives
Category	Redundancy
Complexity	O(n·k) → O(n)

Description

Detects multiple linear scan operations (find, filter, any, contains) on the same collection within a single method. Each scan traverses the collection independently when they could be combined into a single pass or the first result could be cached.

Typical

Order highestTotal = orders.stream().max(Comparator.comparing(Order::getTotal)).orElse(null);
Order firstCancelled = orders.stream().filter(o -> "CANCELLED".equals(o.getStatus())).findFirst().orElse(null);
long paidCount = orders.stream().filter(o -> "PAID".equals(o.getStatus())).count();

After

Order highestTotal = null;
Order firstCancelled = null;
long paidCount = 0;
for (Order o : orders) {
    if (highestTotal == null || o.getTotal().compareTo(highestTotal.getTotal()) > 0) highestTotal = o;
    if (firstCancelled == null && "CANCELLED".equals(o.getStatus())) firstCancelled = o;
    if ("PAID".equals(o.getStatus())) paidCount++;
}

Suggestion

Cache the result of the first lookup, or combine into a single pass