[SPARK-13823][SPARK-13397][SPARK-13395][CORE] More warnings, StandardCharset follow up

## What changes were proposed in this pull request?

Follow up to https://github.com/apache/spark/pull/11657

- Also update `String.getBytes("UTF-8")` to use `StandardCharsets.UTF_8`
- And fix one last new Coverity warning that turned up (use of unguarded `wait()` replaced by simpler/more robust `java.util.concurrent` classes in tests)
- And while we're here cleaning up Coverity warnings, just fix about 15 more build warnings

## How was this patch tested?

Jenkins tests

Author: Sean Owen <sowen@cloudera.com>

Closes #11725 from srowen/SPARK-13823.2.

3 files changed, 7 insertions, 7 deletions

diff --git a/core/src/test/java/org/apache/spark/JavaAPISuite.java b/core/src/test/java/org/apache/spark/JavaAPISuite.java
index a7e74c0079..c1036b8fac 100644
--- a/core/src/test/java/org/apache/spark/JavaAPISuite.java
+++ b/core/src/test/java/org/apache/spark/JavaAPISuite.java
@@ -1068,8 +1068,8 @@ public class JavaAPISuite implements Serializable {
 
   @Test
   public void wholeTextFiles() throws Exception {
-    byte[] content1 = "spark is easy to use.\n".getBytes("utf-8");
-    byte[] content2 = "spark is also easy to use.\n".getBytes("utf-8");
+    byte[] content1 = "spark is easy to use.\n".getBytes(StandardCharsets.UTF_8);
+    byte[] content2 = "spark is also easy to use.\n".getBytes(StandardCharsets.UTF_8);
 
     String tempDirName = tempDir.getAbsolutePath();
     Files.write(content1, new File(tempDirName + "/part-00000"));
@@ -1131,7 +1131,7 @@ public class JavaAPISuite implements Serializable {
   @Test
   public void binaryFiles() throws Exception {
     // Reusing the wholeText files example
-    byte[] content1 = "spark is easy to use.\n".getBytes("utf-8");
+    byte[] content1 = "spark is easy to use.\n".getBytes(StandardCharsets.UTF_8);
 
     String tempDirName = tempDir.getAbsolutePath();
     File file1 = new File(tempDirName + "/part-00000");
@@ -1152,7 +1152,7 @@ public class JavaAPISuite implements Serializable {
   @Test
   public void binaryFilesCaching() throws Exception {
     // Reusing the wholeText files example
-    byte[] content1 = "spark is easy to use.\n".getBytes("utf-8");
+    byte[] content1 = "spark is easy to use.\n".getBytes(StandardCharsets.UTF_8);
 
     String tempDirName = tempDir.getAbsolutePath();
     File file1 = new File(tempDirName + "/part-00000");
@@ -1181,7 +1181,7 @@ public class JavaAPISuite implements Serializable {
   @Test
   public void binaryRecords() throws Exception {
     // Reusing the wholeText files example
-    byte[] content1 = "spark isn't always easy to use.\n".getBytes("utf-8");
+    byte[] content1 = "spark isn't always easy to use.\n".getBytes(StandardCharsets.UTF_8);
     int numOfCopies = 10;
     String tempDirName = tempDir.getAbsolutePath();
     File file1 = new File(tempDirName + "/part-00000");
diff --git a/core/src/test/java/org/apache/spark/shuffle/sort/ShuffleInMemorySorterSuite.java b/core/src/test/java/org/apache/spark/shuffle/sort/ShuffleInMemorySorterSuite.java
index a3502708aa..4cd3600df1 100644
--- a/core/src/test/java/org/apache/spark/shuffle/sort/ShuffleInMemorySorterSuite.java
+++ b/core/src/test/java/org/apache/spark/shuffle/sort/ShuffleInMemorySorterSuite.java
@@ -80,7 +80,7 @@ public class ShuffleInMemorySorterSuite {
         sorter.expandPointerArray(consumer.allocateArray(sorter.numRecords() * 2));
       }
       final long recordAddress = memoryManager.encodePageNumberAndOffset(dataPage, position);
-      final byte[] strBytes = str.getBytes("utf-8");
+      final byte[] strBytes = str.getBytes(StandardCharsets.UTF_8);
       Platform.putInt(baseObject, position, strBytes.length);
       position += 4;
       Platform.copyMemory(
diff --git a/core/src/test/java/org/apache/spark/util/collection/unsafe/sort/UnsafeInMemorySorterSuite.java b/core/src/test/java/org/apache/spark/util/collection/unsafe/sort/UnsafeInMemorySorterSuite.java
index 90849ab0bd..483319434d 100644
--- a/core/src/test/java/org/apache/spark/util/collection/unsafe/sort/UnsafeInMemorySorterSuite.java
+++ b/core/src/test/java/org/apache/spark/util/collection/unsafe/sort/UnsafeInMemorySorterSuite.java
@@ -80,7 +80,7 @@ public class UnsafeInMemorySorterSuite {
     // Write the records into the data page:
     long position = dataPage.getBaseOffset();
     for (String str : dataToSort) {
-      final byte[] strBytes = str.getBytes("utf-8");
+      final byte[] strBytes = str.getBytes(StandardCharsets.UTF_8);
       Platform.putInt(baseObject, position, strBytes.length);
       position += 4;
       Platform.copyMemory(