public static Field getDeclaredField(Class objectClass, String fieldName) {
        Map<String, Field> fieldMap = fieldMapCache.get(objectClass);
        if (fieldMap == null) {
            Map<String, Field> map = new HashMap<>();
            declaredFields(objectClass, field -> map.put(field.getName(), field));

            fieldMapCache.putIfAbsent(objectClass, map);
            fieldMap = fieldMapCache.get(objectClass);
        }

        return fieldMap.get(fieldName);
    }
@author Bob Lee
@author Jesse Wilson
@author Shaojin Wen
@author poo0054
core/src/main/java/com/alibaba/fastjson2/util/BeanUtils.java