stream filter distinct

함수 생성

/*
 * distinct
 */
public static <T> Predicate<T> distinctByKey(Function<? super T, ?> keyExtractor) {
    Set<Object> seen = ConcurrentHashMap.newKeySet();
    return t -> seen.add(keyExtractor.apply(t));
}

사용

List<Member> list = ....
list = list.stream().filter(distinctByKey(Member::getId)).collect(Collectors.toList());