[SPARK-6428] Turn on explicit type checking for public methods.

This builds on my earlier pull requests and turns on the explicit type checking in scalastyle.

Author: Reynold Xin <rxin@databricks.com>

Closes #5342 from rxin/SPARK-6428 and squashes the following commits:

7b531ab [Reynold Xin] import ordering
2d9a8a5 [Reynold Xin] jl
e668b1c [Reynold Xin] override
9b9e119 [Reynold Xin] Parenthesis.
82e0cf5 [Reynold Xin] [SPARK-6428] Turn on explicit type checking for public methods.

2 files changed, 5 insertions, 4 deletions

diff --git a/external/kafka/src/main/scala/org/apache/spark/streaming/kafka/DirectKafkaInputDStream.scala b/external/kafka/src/main/scala/org/apache/spark/streaming/kafka/DirectKafkaInputDStream.scala
index 04e65cb3d7..1b1fc8051d 100644
--- a/external/kafka/src/main/scala/org/apache/spark/streaming/kafka/DirectKafkaInputDStream.scala
+++ b/external/kafka/src/main/scala/org/apache/spark/streaming/kafka/DirectKafkaInputDStream.scala
@@ -129,8 +129,9 @@ class DirectKafkaInputDStream[
 
   private[streaming]
   class DirectKafkaInputDStreamCheckpointData extends DStreamCheckpointData(this) {
-    def batchForTime = data.asInstanceOf[mutable.HashMap[
-      Time, Array[OffsetRange.OffsetRangeTuple]]]
+    def batchForTime: mutable.HashMap[Time, Array[(String, Int, Long, Long)]] = {
+      data.asInstanceOf[mutable.HashMap[Time, Array[OffsetRange.OffsetRangeTuple]]]
+    }
 
     override def update(time: Time) {
       batchForTime.clear()
diff --git a/external/kafka/src/main/scala/org/apache/spark/streaming/kafka/KafkaRDD.scala b/external/kafka/src/main/scala/org/apache/spark/streaming/kafka/KafkaRDD.scala
index 6d465bcb6b..4a83b715fa 100644
--- a/external/kafka/src/main/scala/org/apache/spark/streaming/kafka/KafkaRDD.scala
+++ b/external/kafka/src/main/scala/org/apache/spark/streaming/kafka/KafkaRDD.scala
@@ -155,7 +155,7 @@ class KafkaRDD[
         .dropWhile(_.offset < requestOffset)
     }
 
-    override def close() = consumer.close()
+    override def close(): Unit = consumer.close()
 
     override def getNext(): R = {
       if (iter == null || !iter.hasNext) {
@@ -207,7 +207,7 @@ object KafkaRDD {
       fromOffsets: Map[TopicAndPartition, Long],
       untilOffsets: Map[TopicAndPartition, LeaderOffset],
       messageHandler: MessageAndMetadata[K, V] => R
-  ): KafkaRDD[K, V, U, T, R] = {
+    ): KafkaRDD[K, V, U, T, R] = {
     val leaders = untilOffsets.map { case (tp, lo) =>
         tp -> (lo.host, lo.port)
     }.toMap