Externalizable or Serializable?

The advantage of Serializable is it's incredibly easy to implement, and resilient to change (in most cases all you have to do is update the serialversionUID). Externalizable requires the programmer to actually do work, and do more work every time the contents of the class change. As the article you link to points out implementing Externalizable is also error-prone. So from the point of view of utilizing limited programmer time, often Serializable is a better choice. \n\nThe good thing about how Serializable and Externalizable are designed is that you can defer the decision to implement Externalizable until it becomes evident there's a performance problem, and you can selectively implement it only for those classes where there's a problem.",

Serializable is a marker interface that indicates that instances can be written to an output stream and read back. You don't have to write and code (you just have to ensure all fields are themselves Serializable).\n\nExternalizable is a Serializable that alos provides custom (de)serialization code.",