Core Java API 
Package Description
org.apache.spark.api.java
Spark Java programming APIs.
org.apache.spark.api.java.function
Set of interfaces to represent functions in Spark's Java API.
Spark Streaming 
Package Description
org.apache.spark.streaming.api.java
Java APIs for spark streaming.
org.apache.spark.streaming.flume
Spark streaming receiver for Flume.
org.apache.spark.streaming.kafka
Kafka receiver for spark streaming.
org.apache.spark.streaming.mqtt
MQTT receiver for Spark Streaming.
org.apache.spark.streaming.twitter
Twitter feed receiver for spark streaming.
org.apache.spark.streaming.zeromq
Zeromq receiver for spark streaming.
MLlib 
Package Description
org.apache.spark.mllib.classification  
org.apache.spark.mllib.clustering  
org.apache.spark.mllib.linalg  
org.apache.spark.mllib.linalg.distributed  
org.apache.spark.mllib.optimization  
org.apache.spark.mllib.recommendation  
org.apache.spark.mllib.regression  
org.apache.spark.mllib.stat  
org.apache.spark.mllib.tree  
org.apache.spark.mllib.tree.configuration  
org.apache.spark.mllib.tree.impurity  
org.apache.spark.mllib.tree.model  
org.apache.spark.mllib.util  
Spark SQL 
Package Description
org.apache.spark.sql.api.java  
org.apache.spark.sql.hive.api.java  
Other Packages 
Package Description
org.apache.spark
Core Spark classes in Scala.
org.apache.spark.annotation
Spark annotations to mark an API experimental or intended only for advanced usages by developers.
org.apache.spark.broadcast
Spark's broadcast variables, used to broadcast immutable datasets to all nodes.
org.apache.spark.io
IO codecs used for compression.
org.apache.spark.mllib.evaluation  
org.apache.spark.partial  
org.apache.spark.rdd
Provides implementation's of various RDDs.
org.apache.spark.scheduler
Spark's DAG scheduler.
org.apache.spark.serializer
Pluggable serializers for RDD and shuffle data.
org.apache.spark.sql  
org.apache.spark.sql.execution  
org.apache.spark.sql.hive  
org.apache.spark.sql.hive.execution  
org.apache.spark.sql.hive.test  
org.apache.spark.sql.parquet  
org.apache.spark.sql.test  
org.apache.spark.storage  
org.apache.spark.streaming  
org.apache.spark.streaming.dstream
Various implementations of DStreams.
org.apache.spark.streaming.receiver  
org.apache.spark.streaming.scheduler  
org.apache.spark.ui.env  
org.apache.spark.ui.exec  
org.apache.spark.ui.jobs  
org.apache.spark.ui.storage  
org.apache.spark.util
Spark utilities.
org.apache.spark.util.random
Utilities for random number generation.