[MINOR][DOCS] Replace remaining 'sqlContext' in ScalaDoc/JavaDoc.

## What changes were proposed in this pull request?

According to the recent change, this PR replaces all the remaining `sqlContext` usage with `spark` in ScalaDoc/JavaDoc (.scala/.java files) except `SQLContext.scala`, `SparkPlan.scala', and `DatasetHolder.scala`.

## How was this patch tested?

Manual.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #13125 from dongjoon-hyun/minor_doc_sparksession.

6 files changed, 15 insertions, 15 deletions

diff --git a/mllib/src/main/scala/org/apache/spark/ml/feature/package.scala b/mllib/src/main/scala/org/apache/spark/ml/feature/package.scala
index 4571ab2680..b94187ae78 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/feature/package.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/feature/package.scala
@@ -44,7 +44,7 @@ import org.apache.spark.sql.DataFrame
  *   import org.apache.spark.ml.Pipeline
  *
  *   // a DataFrame with three columns: id (integer), text (string), and rating (double).
- *   val df = sqlContext.createDataFrame(Seq(
+ *   val df = spark.createDataFrame(Seq(
  *     (0, "Hi I heard about Spark", 3.0),
  *     (1, "I wish Java could use case classes", 4.0),
  *     (2, "Logistic regression models are neat", 4.0)
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/DataFrameReader.scala b/sql/core/src/main/scala/org/apache/spark/sql/DataFrameReader.scala
index e1a64dfc5e..011aff4ff6 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/DataFrameReader.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/DataFrameReader.scala
@@ -446,10 +446,10 @@ class DataFrameReader private[sql](sparkSession: SparkSession) extends Logging {
    * Each line in the text file is a new row in the resulting Dataset. For example:
    * {{{
    *   // Scala:
-   *   sqlContext.read.text("/path/to/spark/README.md")
+   *   spark.read.text("/path/to/spark/README.md")
    *
    *   // Java:
-   *   sqlContext.read().text("/path/to/spark/README.md")
+   *   spark.read().text("/path/to/spark/README.md")
    * }}}
    *
    * @param paths input path
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/DataFrameStatFunctions.scala b/sql/core/src/main/scala/org/apache/spark/sql/DataFrameStatFunctions.scala
index 3eb1f0f0d5..1855eab96e 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/DataFrameStatFunctions.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/DataFrameStatFunctions.scala
@@ -160,8 +160,8 @@ final class DataFrameStatFunctions private[sql](df: DataFrame) {
    * @return A DataFrame containing for the contingency table.
    *
    * {{{
-   *    val df = sqlContext.createDataFrame(Seq((1, 1), (1, 2), (2, 1), (2, 1), (2, 3), (3, 2),
-   *      (3, 3))).toDF("key", "value")
+   *    val df = spark.createDataFrame(Seq((1, 1), (1, 2), (2, 1), (2, 1), (2, 3), (3, 2), (3, 3)))
+   *      .toDF("key", "value")
    *    val ct = df.stat.crosstab("key", "value")
    *    ct.show()
    *    +---------+---+---+---+
@@ -197,7 +197,7 @@ final class DataFrameStatFunctions private[sql](df: DataFrame) {
    *    val rows = Seq.tabulate(100) { i =>
    *      if (i % 2 == 0) (1, -1.0) else (i, i * -1.0)
    *    }
-   *    val df = sqlContext.createDataFrame(rows).toDF("a", "b")
+   *    val df = spark.createDataFrame(rows).toDF("a", "b")
    *    // find the items with a frequency greater than 0.4 (observed 40% of the time) for columns
    *    // "a" and "b"
    *    val freqSingles = df.stat.freqItems(Array("a", "b"), 0.4)
@@ -258,7 +258,7 @@ final class DataFrameStatFunctions private[sql](df: DataFrame) {
    *    val rows = Seq.tabulate(100) { i =>
    *      if (i % 2 == 0) (1, -1.0) else (i, i * -1.0)
    *    }
-   *    val df = sqlContext.createDataFrame(rows).toDF("a", "b")
+   *    val df = spark.createDataFrame(rows).toDF("a", "b")
    *    // find the items with a frequency greater than 0.4 (observed 40% of the time) for columns
    *    // "a" and "b"
    *    val freqSingles = df.stat.freqItems(Seq("a", "b"), 0.4)
@@ -314,7 +314,7 @@ final class DataFrameStatFunctions private[sql](df: DataFrame) {
    * @return a new [[DataFrame]] that represents the stratified sample
    *
    * {{{
-   *    val df = sqlContext.createDataFrame(Seq((1, 1), (1, 2), (2, 1), (2, 1), (2, 3), (3, 2),
+   *    val df = spark.createDataFrame(Seq((1, 1), (1, 2), (2, 1), (2, 1), (2, 3), (3, 2),
    *      (3, 3))).toDF("key", "value")
    *    val fractions = Map(1 -> 1.0, 3 -> 0.5)
    *    df.stat.sampleBy("key", fractions, 36L).show()
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/ExperimentalMethods.scala b/sql/core/src/main/scala/org/apache/spark/sql/ExperimentalMethods.scala
index a49da6dc2b..a435734b0c 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/ExperimentalMethods.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/ExperimentalMethods.scala
@@ -27,7 +27,7 @@ import org.apache.spark.sql.catalyst.rules.Rule
  * regarding binary compatibility and source compatibility of methods here.
  *
  * {{{
- *   sqlContext.experimental.extraStrategies += ...
+ *   spark.experimental.extraStrategies += ...
  * }}}
  *
  * @since 1.3.0
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/PartitioningAwareFileCatalog.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/PartitioningAwareFileCatalog.scala
index e0e4ddc30b..406d2e8e81 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/PartitioningAwareFileCatalog.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/PartitioningAwareFileCatalog.scala
@@ -168,17 +168,17 @@ abstract class PartitioningAwareFileCatalog(
    *
    * By default, the paths of the dataset provided by users will be base paths.
    * Below are three typical examples,
-   * Case 1) `sqlContext.read.parquet("/path/something=true/")`: the base path will be
+   * Case 1) `spark.read.parquet("/path/something=true/")`: the base path will be
    * `/path/something=true/`, and the returned DataFrame will not contain a column of `something`.
-   * Case 2) `sqlContext.read.parquet("/path/something=true/a.parquet")`: the base path will be
+   * Case 2) `spark.read.parquet("/path/something=true/a.parquet")`: the base path will be
    * still `/path/something=true/`, and the returned DataFrame will also not contain a column of
    * `something`.
-   * Case 3) `sqlContext.read.parquet("/path/")`: the base path will be `/path/`, and the returned
+   * Case 3) `spark.read.parquet("/path/")`: the base path will be `/path/`, and the returned
    * DataFrame will have the column of `something`.
    *
    * Users also can override the basePath by setting `basePath` in the options to pass the new base
    * path to the data source.
-   * For example, `sqlContext.read.option("basePath", "/path/").parquet("/path/something=true/")`,
+   * For example, `spark.read.option("basePath", "/path/").parquet("/path/something=true/")`,
    * and the returned DataFrame will have the column of `something`.
    */
   private def basePaths: Set[Path] = {
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/functions.scala b/sql/core/src/main/scala/org/apache/spark/sql/functions.scala
index 07f55042ee..65bc043076 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/functions.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/functions.scala
@@ -2952,8 +2952,8 @@ object functions {
    *  import org.apache.spark.sql._
    *
    *  val df = Seq(("id1", 1), ("id2", 4), ("id3", 5)).toDF("id", "value")
-   *  val sqlContext = df.sqlContext
-   *  sqlContext.udf.register("simpleUDF", (v: Int) => v * v)
+   *  val spark = df.sparkSession
+   *  spark.udf.register("simpleUDF", (v: Int) => v * v)
    *  df.select($"id", callUDF("simpleUDF", $"value"))
    * }}}
    *