Java based UDF has mandatory functions ? in XI interview questions

Hi !

I've read some XI interview questions in this forum, one says:

Q: what is UDF? What are the mandatory functions that you use in a Java based UDF?

A: Mandatory functions: Init() , Execute(), Destroy(), Run(), SetParameter()

Anyone knows what is talking this question about ? maybe java mapping instead of java udf?

Thanks,

Matias.