What is a serialVersionUID and why should I use it? Eclipse issues warnings when a serialVersionUID is missing.       The serializable class Foo does not declare a static final serialVersionUID field of type long What is serialVersionUID and why is it important? Please show an example where missing serialVersionUID will cause a problem. Answer: The docs for java.io.Serializable are probably about as good an explanation as you'll get: The serialization runtime associates with each serializable class a version number, called a serialVersionUID, which is used during deserialization to verify