Java :: Map loop 사용하기

/* 방법1 */
for (Map.Entry<String, Long> element : amounts.entrySet()) {
    totalAmount += element.getValue();
}

/* 방법2 */
for (String key : amounts.keySet()) {
    totalAmount += amounts.get(key);
}

/* 방법3 */
Iterator<String> keys = amounts.keySet().iterator();
while (keys.hasNext()) {
    String key = keys.next();
    totalAmount += amounts.get(key);
}

매번 까먹음..