[MINOR][SQL] Fix comments styl and correct several styles and nits in CSV data source

## What changes were proposed in this pull request?

While trying to create a PR (which was not an issue at the end), I just corrected some style nits.

So, I removed the changes except for some coding style corrections.

- According to the [scala-style-guide#documentation-style](https://github.com/databricks/scala-style-guide#documentation-style), Scala style comments are discouraged.

>```scala
>/** This is a correct one-liner, short description. */
>
>/**
>  * This is correct multi-line JavaDoc comment. And
>  * this is my second line, and if I keep typing, this would be
>  * my third line.
>  */
>
>/** In Spark, we don't use the ScalaDoc style so this
>   * is not correct.
>   */
>```

- Double newlines between consecutive methods was removed. According to [scala-style-guide#blank-lines-vertical-whitespace](https://github.com/databricks/scala-style-guide#blank-lines-vertical-whitespace), single newline appears when

>Between consecutive members (or initializers) of a class: fields, constructors, methods, nested classes, static initializers, instance initializers.

- Remove uesless parentheses in tests

- Use `mapPartitions` instead of `mapPartitionsWithIndex()`.

## How was this patch tested?

Unit tests were used and `dev/run_tests` for style tests.

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #12109 from HyukjinKwon/SPARK-14271.

1 files changed, 5 insertions, 5 deletions

diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/csv/CSVParserSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/csv/CSVParserSuite.scala
index c0c38c6787..dc54883277 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/csv/CSVParserSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/csv/CSVParserSuite.scala
@@ -46,7 +46,7 @@ class CSVParserSuite extends SparkFunSuite {
     var numRead = 0
       var n = 0
       do { // try to fill cbuf
-      var off = 0
+        var off = 0
         var len = cbuf.length
         n = reader.read(cbuf, off, len)
 
@@ -81,7 +81,7 @@ class CSVParserSuite extends SparkFunSuite {
   test("Regular case") {
     val input = List("This is a string", "This is another string", "Small", "", "\"quoted\"")
     val read = readAll(input.toIterator)
-    assert(read === input.mkString("\n") ++ ("\n"))
+    assert(read === input.mkString("\n") ++ "\n")
   }
 
   test("Empty iter") {
@@ -93,12 +93,12 @@ class CSVParserSuite extends SparkFunSuite {
   test("Embedded new line") {
     val input = List("This is a string", "This is another string", "Small\n", "", "\"quoted\"")
     val read = readAll(input.toIterator)
-    assert(read === input.mkString("\n") ++ ("\n"))
+    assert(read === input.mkString("\n") ++ "\n")
   }
 
   test("Buffer Regular case") {
     val input = List("This is a string", "This is another string", "Small", "", "\"quoted\"")
-    val output = input.mkString("\n") ++ ("\n")
+    val output = input.mkString("\n") ++ "\n"
     for(i <- 1 to output.length + 5) {
       val read = readBufAll(input.toIterator, i)
       assert(read === output)
@@ -116,7 +116,7 @@ class CSVParserSuite extends SparkFunSuite {
 
   test("Buffer Embedded new line") {
     val input = List("This is a string", "This is another string", "Small\n", "", "\"quoted\"")
-    val output = input.mkString("\n") ++ ("\n")
+    val output = input.mkString("\n") ++ "\n"
     for(i <- 1 to output.length + 5) {
       val read = readBufAll(input.toIterator, 1)
       assert(read === output)