Repeated Collection Iteration¶

Rule details


Rule ID	`repeated-collection-iteration`
Severity	INFO — worth knowing, may not matter at your scale
Confidence	LOW — heuristic-heavy, may produce false positives
Category	Redundancy
Complexity	O(k·n) → O(n)

Flags multiple passes over the same collection that could potentially be fused into a single pass.

What it detects¶

Two stream pipelines on the same source:

double total = orders.stream().mapToDouble(Order::getAmount).sum();
long count = orders.stream().filter(o -> o.getAmount() > 100).count();
// Two passes over orders — could be one

Two for-each loops over the same collection:

for (Item item : items) { validate(item); }
for (Item item : items) { transform(item); }
// Could combine into a single loop

What it skips¶

Streams on different collections (independent operations)
Streams in mutually exclusive branches (if/else — only one executes)

Why INFO severity¶

Multiple passes are often intentional for readability. Two clear, separate pipelines can be easier to understand than one combined pipeline. This rule surfaces the opportunity; the developer decides if fusing is worth the readability tradeoff.

Fix¶

Combine into a single pass when the operations are compatible:

double total = 0;
long count = 0;
for (Order o : orders) {
    total += o.getAmount();
    if (o.getAmount() > 100) count++;
}