Core Java API

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

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.kinesis
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

org.apache.spark.ml	Spark ML is a BETA component that adds a new set of machine learning APIs to let users quickly assemble and configure practical machine learning pipelines.
org.apache.spark.ml.attribute	ML attributes
org.apache.spark.ml.classification
org.apache.spark.ml.evaluation
org.apache.spark.ml.feature
org.apache.spark.ml.param
org.apache.spark.ml.recommendation
org.apache.spark.ml.regression
org.apache.spark.ml.tuning
org.apache.spark.mllib.classification
org.apache.spark.mllib.clustering
org.apache.spark.mllib.evaluation
org.apache.spark.mllib.feature
org.apache.spark.mllib.linalg
org.apache.spark.mllib.linalg.distributed
org.apache.spark.mllib.optimization
org.apache.spark.mllib.random
org.apache.spark.mllib.rdd
org.apache.spark.mllib.recommendation
org.apache.spark.mllib.regression
org.apache.spark.mllib.stat
org.apache.spark.mllib.stat.test
org.apache.spark.mllib.tree
org.apache.spark.mllib.tree.configuration
org.apache.spark.mllib.tree.impurity
org.apache.spark.mllib.tree.loss
org.apache.spark.mllib.tree.model
org.apache.spark.mllib.util

Spark SQL

org.apache.spark.sql.api.java

Allows the execution of relational queries, including those expressed in SQL using Spark.

Other Packages

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.api.r
org.apache.spark.broadcast	Spark's broadcast variables, used to broadcast immutable datasets to all nodes.
org.apache.spark.examples.streaming
org.apache.spark.graphx	ALPHA COMPONENT GraphX is a graph processing framework built on top of Spark.
org.apache.spark.graphx.impl
org.apache.spark.graphx.lib	Various analytics functions for graphs.
org.apache.spark.graphx.util	Collections of utilities used by graphx.
org.apache.spark.input
org.apache.spark.io	IO codecs used for compression.
org.apache.spark.launcher	Library for launching Spark applications.
org.apache.spark.ml.tree
org.apache.spark.mllib.fpm
org.apache.spark.mllib.pmml
org.apache.spark.mllib.stat.distribution
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.scheduler.cluster
org.apache.spark.scheduler.local
org.apache.spark.serializer	Pluggable serializers for RDD and shuffle data.
org.apache.spark.sql
org.apache.spark.sql.expressions
org.apache.spark.sql.hive
org.apache.spark.sql.jdbc
org.apache.spark.sql.json
org.apache.spark.sql.sources
org.apache.spark.sql.test
org.apache.spark.sql.types
org.apache.spark.status.api.v1
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.streaming.ui
org.apache.spark.streaming.util
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.