What does serialVersionUID mean in Java?

In Java, serialVersionUID is a static constant used to provide a version control identifier to the JVM. It is introduced to control the versions of classes during the serialization and deserialization process.

The main purpose of serialVersionUID is to ensure compatibility during the process of serialization and deserialization. When an object is serialized, the serialVersionUID is written into the serialized data. When deserializing the object, the JVM will compare the read serialVersionUID with the serialVersionUID declared in the current class definition. If they do not match, an InvalidClassException exception will be thrown, indicating that the class versions do not match and deserialization cannot proceed.

The value of serialVersionUID is a 64-bit integer that can be manually specified or generated by the compiler based on the class structure. One advantage of manually specifying serialVersionUID is to ensure version compatibility when the class structure changes. If serialVersionUID is not manually specified, the compiler will generate a value based on the class structure, but this can lead to the inability to deserialize objects created before structural changes.

Therefore, the meaning of serialVersionUID is to identify the version of a class in order to correctly match the class version during the process of serialization and deserialization.