实现序列化的接口必须提供无参构造方法，否则在运行时报错。
反序列化的时候，非序列化类会使用无参构造方法将属性初始化。
the default mechanism for restoring the object’s non-static and
non-transient fields
If a serializable class does not explicitly declare a serialVersionUID, then
- the serialization runtime will calculate a default serialVersionUID value
- for that class based on various aspects of the class, as described in the
Java(TM) Object Serialization Specification.
However, it is strongly
- recommended that all serializable classes explicitly declare
- serialVersionUID values, since the default serialVersionUID computation is
- highly sensitive to class details that may vary depending on compiler
- implementations, and can thus result in unexpected