@Override
    public V computeIfAbsent(String key, Function<? super String, ? extends V> mappingFunction) {
        return Map.super.computeIfAbsent(key.toLowerCase(), mappingFunction);
    }
@Test
    void computeIfAbsent() {
        Map<String, Object> map = new LowerCaseLinkHashMap<>(lowerCaseLinkHashMap);
        Object result = map.computeIfAbsent("key", String::toUpperCase);
        Assertions.assertEquals("Value", result);
        Assertions.assertEquals("Value", map.get("key"));

        result = map.computeIfAbsent("computeIfAbsent", String::toUpperCase);
        Assertions.assertEquals("COMPUTEIFABSENT", result);
        Assertions.assertEquals("COMPUTEIFABSENT", map.get("computeIfAbsent"));
    }