What does "Developer API" tag mean in Javadoc/Scaladoc?

Question

Like here for example HadoopRDD:

Can you still use it or not?

Answer 1

Exact meaning of this annotation is explained in its docstring:

A lower-level, unstable API intended for developers.

Developer API's might change or be removed in minor versions of Spark.

So more or less "use at your own risk".

You can also check Separate API annotation into two components: InterfaceAudience & InterfaceStability on developers list for additional details and discussion.