References
Some references are as follows:
http://www.scala-lang.org/api/current/index.html#scala.collection.immutable.List
http://spark.apache.org/docs/latest/api/scala/index.html#org.apache.spark.api.java.JavaRDD
http://spark.apache.org/docs/latest/api/scala/index.html#org.apache.spark.api.java.JavaPairRDD
http://spark.apache.org/docs/latest/api/scala/index.html#org.apache.spark.api.java.JavaDoubleRDD
https://spark.apache.org/docs/latest/api/scala/index.html#org.apache.spark.SparkContext
http://abshinn.github.io/python/apache-spark/2014/10/11/using-combinebykey-in-apache-spark/
Good examples of RDD transformations: (https://github.com/JerryLead/SparkLearning/tree/master/src)