StreamSample.java

private Map<String, Set<Rule>> ruleSets;

@Override
public Rule findRule(String ruleSetName, String route, String method) {
    Set<Rule> rules = ruleSets.get(ruleSetName);
    if (rules == null) 
        rules = new HashSet<>();

    Optional<Rule> detectedRule = rules.stream()
                    .filter(rule -> RouteMatcher.match(rule.getRoute(), route)
                                && rule.getMethod().equals(method))
                    .findFirst();

    return detectedRule.isPresent() ? detectedRule.get() : new DefaultRule();
}

Nějak nevidím žádné for loopy :) ... takže to se streamy jde.
Mohl bys to ještě zkrátit na one-liner:

private Map<String, Set<Rule>> ruleSets;

@Override
public Rule findRule(String ruleSetName, String route, String method) {
    return ruleSets.getOrDefault(ruleSetName, new HashSet<>())
                   .stream()
                   .filter(rule -> RouteMatcher.match(rule.getRoute(), route) && rule.getMethod().equals(method))
                   .findFirst()
                   .orElse(new DefaultRule());
}

Pěkné, díky! 👍 To jsem potřeboval