What means 1L serialVersionUID? When could I use this default value 1L?

Question

There are 3 ways to define the serialVersionUID :

1. private static final long serialVersionUID = 1L; (Default)
2. private static final long serialVersionUID = -         


        

Answer 1

The JVM will throw a InvalidClassException if the serialVersionUID of a serialized object does not match the serialVersionUID of the class it is being deserialized as.

The serialVersionUID of a class should change every time the class changes in an incompatible way. Normally this means every time you change the shape of a class (ie fields or methods change).

There are some cases where you don't want the serialVersionUID to change. For instance you might accept old versions of the object into your application. In this case, you can leave the serialVersionUID the same and new fields will come through as null.