[SPARK-21731][BUILD] Upgrade scalastyle to 0.9.

This version fixes a few issues in the import order checker; it provides
better error messages, and detects more improper ordering (thus the need
to change a lot of files in this patch). The main fix is that it correctly
complains about the order of packages vs. classes.

As part of the above, I moved some "SparkSession" import in ML examples
inside the "$example on$" blocks; that didn't seem consistent across
different source files to start with, and avoids having to add more on/off blocks
around specific imports.

The new scalastyle also seems to have a better header detector, so a few
license headers had to be updated to match the expected indentation.

Author: Marcelo Vanzin <[email protected]>

Closes #18943 from vanzin/SPARK-21731.

Author: Marcelo Vanzin

core/src/main/scala/org/apache/spark/api/java/JavaDoubleRDD.scala

@@ -22,8 +22,8 @@ import java.lang.{Double => JDouble}
 import scala.language.implicitConversions
 import scala.reflect.ClassTag
 
-import org.apache.spark.annotation.Since
 import org.apache.spark.Partitioner
+import org.apache.spark.annotation.Since
 import org.apache.spark.api.java.function.{Function => JFunction}
 import org.apache.spark.partial.{BoundedDouble, PartialResult}
 import org.apache.spark.rdd.RDD

core/src/main/scala/org/apache/spark/api/python/PythonWorkerFactory.scala

@@ -22,8 +22,8 @@ import java.net.{InetAddress, ServerSocket, Socket, SocketException}
 import java.nio.charset.StandardCharsets
 import java.util.Arrays
 
-import scala.collection.mutable
 import scala.collection.JavaConverters._
+import scala.collection.mutable
 
 import org.apache.spark._
 import org.apache.spark.internal.Logging

core/src/main/scala/org/apache/spark/api/r/JVMObjectTracker.scala

@@ -17,8 +17,8 @@
 
 package org.apache.spark.api.r
 
-import java.util.concurrent.atomic.AtomicInteger
 import java.util.concurrent.ConcurrentHashMap
+import java.util.concurrent.atomic.AtomicInteger
 
 /** JVM object ID wrapper */
 private[r] case class JVMObjectId(id: String) {

core/src/main/scala/org/apache/spark/api/r/RBackendHandler.scala

@@ -26,9 +26,9 @@ import io.netty.channel.{ChannelHandlerContext, SimpleChannelInboundHandler}
 import io.netty.channel.ChannelHandler.Sharable
 import io.netty.handler.timeout.ReadTimeoutException
 
+import org.apache.spark.SparkConf
 import org.apache.spark.api.r.SerDe._
 import org.apache.spark.internal.Logging
-import org.apache.spark.SparkConf
 import org.apache.spark.util.{ThreadUtils, Utils}
 
 /**

core/src/main/scala/org/apache/spark/deploy/PythonRunner.scala

@@ -20,8 +20,8 @@ package org.apache.spark.deploy
 import java.io.File
 import java.net.URI
 
-import scala.collection.mutable.ArrayBuffer
 import scala.collection.JavaConverters._
+import scala.collection.mutable.ArrayBuffer
 import scala.util.Try
 
 import org.apache.spark.{SparkConf, SparkUserAppException}

core/src/main/scala/org/apache/spark/deploy/SparkHadoopUtil.scala

@@ -22,8 +22,8 @@ import java.security.PrivilegedExceptionAction
 import java.text.DateFormat
 import java.util.{Arrays, Comparator, Date, Locale}
 
-import scala.collection.immutable.Map
 import scala.collection.JavaConverters._
+import scala.collection.immutable.Map
 import scala.collection.mutable
 import scala.collection.mutable.HashMap
 import scala.util.control.NonFatal

core/src/main/scala/org/apache/spark/deploy/rest/RestSubmissionServer.scala

@@ -11,7 +11,7 @@
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-* See the License for the specific language governing permissions and
+ * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 

core/src/main/scala/org/apache/spark/deploy/rest/StandaloneRestServer.scala

@@ -11,7 +11,7 @@
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-* See the License for the specific language governing permissions and
+ * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 

core/src/main/scala/org/apache/spark/deploy/worker/WorkerArguments.scala

@@ -21,8 +21,8 @@ import java.lang.management.ManagementFactory
 
 import scala.annotation.tailrec
 
-import org.apache.spark.util.{IntParam, MemoryParam, Utils}
 import org.apache.spark.SparkConf
+import org.apache.spark.util.{IntParam, MemoryParam, Utils}
 
 /**
  * Command-line parser for the worker.

core/src/main/scala/org/apache/spark/input/PortableDataStream.scala

@@ -27,9 +27,9 @@ import org.apache.hadoop.fs.Path
 import org.apache.hadoop.mapreduce.{InputSplit, JobContext, RecordReader, TaskAttemptContext}
 import org.apache.hadoop.mapreduce.lib.input.{CombineFileInputFormat, CombineFileRecordReader, CombineFileSplit}
 
-import org.apache.spark.internal.config
 import org.apache.spark.SparkContext
 import org.apache.spark.annotation.Since
+import org.apache.spark.internal.config
 
 /**
  * A general format for reading whole files in as streams, byte arrays,