Iterating over values by Key

I have K/V pairs where V is an Iterable (from previous groupBy). I use the JAVA API. What I want is to iterate over the values by key, and on every element set previousElementId attribute, that is the id of the previous element in the sorted list. I try to do this with mapValues. I create an

NullPointerException in ApplicationMaster

Hi all, I am trying to run a Spark Java application on EMR, but I keep getting NullPointerException from the Application master (spark version on EMR: 1.2). The stacktrace is below. I also tried to run the application on Hortonworks Sandbox (2.2) with spark 1.2, following the blogpost