What is serialVersionUID explained in detail?

The serialVersionUID is a static constant used in the Java serialization mechanism. When a class implements the Serializable interface, each instance of that class has its own serialVersionUID. This serialVersionUID is used to identify the version of the class and ensure that objects can be serialized and deserialized with compatibility.

During the serialization process, Java converts an object into a series of bytes for transmission over a network or saving to a file. When the recipient wants to deserialize the received bytes, Java checks if the serialized bytes match the serialVersionUID of the current class. If they match, the object is considered trustworthy and can be deserialized normally. If they do not match, Java throws an InvalidClassException, indicating that the object’s version is not consistent and cannot be deserialized.

The purpose of serialVersionUID is to maintain compatibility for serialization and deserialization when the structure of a class changes. If the structure of a class changes, such as by adding, removing, or modifying fields or methods, Java will generate a new serialVersionUID based on the class structure. If serialVersionUID is not set manually, the new serialVersionUID will be different from the old one, leading to deserialization failure. To maintain compatibility, you can manually set the serialVersionUID to match the one from the old version.

In summary, serialVersionUID is a constant used to identify the version number of a class, allowing for compatibility in Java serialization and deserialization.