In Java, the parent class is serialized, but does the subclass still need to be implemented?

The

Java parent class implements serialization, but does the subclass still need to be implemented?
what is the best way to serialize parent and child classes?
does an inner class need to be serialized when it is used by an external class?
and, how do you write serialization id? is it random?
ask everyone for advice with an open mind.

Apr.09,2021
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1eb97b1-275d.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1eb97b1-275d.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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