[SPARK-13823][CORE][STREAMING][SQL] Always specify Charset in String <-> byte[] conversions (and remaining Coverity items)

## What changes were proposed in this pull request?

- Fixes calls to `new String(byte[])` or `String.getBytes()` that rely on platform default encoding, to use UTF-8
- Same for `InputStreamReader` and `OutputStreamWriter` constructors
- Standardizes on UTF-8 everywhere
- Standardizes specifying the encoding with `StandardCharsets.UTF-8`, not the Guava constant or "UTF-8" (which means handling `UnuspportedEncodingException`)
- (also addresses the other remaining Coverity scan issues, which are pretty trivial; these are separated into commit https://github.com/srowen/spark/commit/1deecd8d9ca986d8adb1a42d315890ce5349d29c )

## How was this patch tested?

Jenkins tests

Author: Sean Owen <sowen@cloudera.com>

Closes #11657 from srowen/SPARK-13823.

1 files changed, 2 insertions, 8 deletions

diff --git a/common/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java b/common/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
index 427a8315e0..e16166ade4 100644
--- a/common/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
+++ b/common/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
@@ -21,6 +21,7 @@ import javax.annotation.Nonnull;
 import java.io.*;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
+import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.Map;
 
@@ -825,14 +826,7 @@ public final class UTF8String implements Comparable<UTF8String>, Externalizable,
 
   @Override
   public String toString() {
-    try {
-      return new String(getBytes(), "utf-8");
-    } catch (UnsupportedEncodingException e) {
-      // Turn the exception into unchecked so we can find out about it at runtime, but
-      // don't need to add lots of boilerplate code everywhere.
-      throwException(e);
-      return "unknown";  // we will never reach here.
-    }
+    return new String(getBytes(), StandardCharsets.UTF_8);
   }
 
   @Override