[SPARK-9534] [BUILD] Enable javac lint for scalac parity; fix a lot of build warnings, 1.5.0 edition

Enable most javac lint warnings; fix a lot of build warnings. In a few cases, touch up surrounding code in the process.

I'll explain several of the changes inline in comments.

Author: Sean Owen <sowen@cloudera.com>

Closes #7862 from srowen/SPARK-9534 and squashes the following commits:

ea51618 [Sean Owen] Enable most javac lint warnings; fix a lot of build warnings. In a few cases, touch up surrounding code in the process.

1 files changed, 1 insertions, 1 deletions

diff --git a/external/kafka/src/test/java/org/apache/spark/streaming/kafka/JavaDirectKafkaStreamSuite.java b/external/kafka/src/test/java/org/apache/spark/streaming/kafka/JavaDirectKafkaStreamSuite.java
index 02cd24a359..9db07d0507 100644
--- a/external/kafka/src/test/java/org/apache/spark/streaming/kafka/JavaDirectKafkaStreamSuite.java
+++ b/external/kafka/src/test/java/org/apache/spark/streaming/kafka/JavaDirectKafkaStreamSuite.java
@@ -70,7 +70,7 @@ public class JavaDirectKafkaStreamSuite implements Serializable {
     final String topic1 = "topic1";
     final String topic2 = "topic2";
     // hold a reference to the current offset ranges, so it can be used downstream
-    final AtomicReference<OffsetRange[]> offsetRanges = new AtomicReference();
+    final AtomicReference<OffsetRange[]> offsetRanges = new AtomicReference<>();
 
     String[] topic1data = createTopicAndSendData(topic1);
     String[] topic2data = createTopicAndSendData(topic2);