[SPARK-16816] Modify java example which is also reflect in documentation exmaple

## What changes were proposed in this pull request?

Modify java example which is also reflect in document.

## How was this patch tested?

run test cases.

Author: sandy <phalodi@gmail.com>

Closes #14436 from phalodi/SPARK-16816.

Author: phalodi

examples/src/main/java/org/apache/spark/examples/sql/JavaSQLDataSourceExample.java

@@ -19,10 +19,13 @@
 // $example on:schema_merging$
 import java.io.Serializable;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 // $example off:schema_merging$
 
 // $example on:basic_parquet_example$
+import org.apache.spark.api.java.JavaRDD;
+import org.apache.spark.api.java.JavaSparkContext;
 import org.apache.spark.api.java.function.MapFunction;
 import org.apache.spark.sql.Encoders;
 // $example on:schema_merging$
@@ -213,6 +216,19 @@ private static void runJsonDatasetExample(SparkSession spark) {
     // +------+
     // |Justin|
     // +------+
+
+    // Alternatively, a DataFrame can be created for a JSON dataset represented by
+    // an RDD[String] storing one JSON object per string.
+    List<String> jsonData = Arrays.asList(
+            "{\"name\":\"Yin\",\"address\":{\"city\":\"Columbus\",\"state\":\"Ohio\"}}");
+    JavaRDD<String> anotherPeopleRDD = new JavaSparkContext(spark.sparkContext()).parallelize(jsonData);
+    Dataset anotherPeople = spark.read().json(anotherPeopleRDD);
+    anotherPeople.show();
+    // +---------------+----+
+    // |        address|name|
+    // +---------------+----+
+    // |[Columbus,Ohio]| Yin|
+    // +---------------+----+
     // $example off:json_dataset$
   }