Prefer empty collection constant (ARCH4088)

Key java.performance.prefer-empty-collection-constant · Severity info · Category performance

Returning a fresh empty collection on every call is a needless allocation. Collections.emptyList() or List.of() returns an immutable, shared instance and avoids the allocation.

Incorrect

public List<String> tags() {
    if (raw == null) {
        return new ArrayList<>();
    }
    return parse(raw);
}

Correct

public List<String> tags() {
    if (raw == null) {
        return List.of();
    }
    return parse(raw);
}

Fix

Return List.of() or Collections.emptyList() instead of new ArrayList<>() for empty results.