[MINOR] Resolve a number of miscellaneous build warnings

## What changes were proposed in this pull request?

This change resolves a number of build warnings that have accumulated, before 2.x. It does not address a large number of deprecation warnings, especially related to the Accumulator API. That will happen separately.

## How was this patch tested?

Jenkins

Author: Sean Owen <sowen@cloudera.com>

Closes #13377 from srowen/BuildWarnings.

1 files changed, 2 insertions, 2 deletions

diff --git a/common/unsafe/src/main/java/org/apache/spark/unsafe/Platform.java b/common/unsafe/src/main/java/org/apache/spark/unsafe/Platform.java
index bdf52f32c6..77c8c398be 100644
--- a/common/unsafe/src/main/java/org/apache/spark/unsafe/Platform.java
+++ b/common/unsafe/src/main/java/org/apache/spark/unsafe/Platform.java
@@ -155,8 +155,8 @@ public final class Platform {
   @SuppressWarnings("unchecked")
   public static ByteBuffer allocateDirectBuffer(int size) {
     try {
-      Class cls = Class.forName("java.nio.DirectByteBuffer");
-      Constructor constructor = cls.getDeclaredConstructor(Long.TYPE, Integer.TYPE);
+      Class<?> cls = Class.forName("java.nio.DirectByteBuffer");
+      Constructor<?> constructor = cls.getDeclaredConstructor(Long.TYPE, Integer.TYPE);
       constructor.setAccessible(true);
       Field cleanerField = cls.getDeclaredField("cleaner");
       cleanerField.setAccessible(true);