SerialVersionUID in Java 1.4.2 and 1.5

Question

Hi!!!
Just ny curiosity: I�ve took a look at the API documentation for Java 1.5 and, as you can see here in [url http://java.sun.com/j2se/1.5.0/docs/api/java/io/Serializable.html]Serializable★, according to the documentation:
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, [i]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 InvalidClassExceptions during deserialization. Therefore, to guarantee a consistent serialVersionUID value across different java compiler implementations, a serializable class must declare an explicit serialVersionUID value. It is also strongly advised that explicit serialVersionUID declarations use the private modifier where possible, since such declarations apply only to the immediately declaring class--serialVersionUID fields are not useful as inherited members.
Well, the fact is that in API Docs for [url http://java.sun.com/j2se/1.4.2/docs/api/java/io/Serializable.html]1.4.2 version★ this excerpt does not exist. What does it mean? Would it mean that in 1.4.2 serialVersionUID was not really necessary, and now, with 1.5, it is? Or would Sun simply forget to rewrite the 1.4.2 API Docs, in order to be in conformity with 1.5 Docs?

Answer 1

Well, they wouldn't rewrite their 1.4 documents at all actually.
This is just Sun improving their product's documentation. Defining a serialVersionUID has always been a good idea, as all versions of the Serialization Specification show.