public static Map<String, Object> replaceKeyCharacter(Map<String, Object> map, char oldChar, char newChar) {
        final Map<String, Object> result = new HashMap<>(map.size());
        for (Map.Entry<String, Object> entry : map.entrySet()) {
            final String key = entry.getKey().replace(oldChar, newChar);
            final Object value = entry.getValue();
            result.put(key, value);
        }
        return result;
    }
@Test
    public void replaceKeyCharacterHandlesEmptyMap() {
        assertThat(MapUtils.replaceKeyCharacter(Collections.emptyMap(), '.', '_')).isEmpty();
    }