[SPARK-15398][ML] Update the warning message to recommend ML usage

## What changes were proposed in this pull request?
MLlib are not recommended to use, and some methods are even deprecated.
Update the warning message to recommend ML usage.
```
  def showWarning() {
    System.err.println(
      """WARN: This is a naive implementation of Logistic Regression and is given as an example!
        |Please use either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
        |org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS
        |for more conventional use.
      """.stripMargin)
  }
```
To
```
  def showWarning() {
    System.err.println(
      """WARN: This is a naive implementation of Logistic Regression and is given as an example!
        |Please use org.apache.spark.ml.classification.LogisticRegression
        |for more conventional use.
      """.stripMargin)
  }
```

## How was this patch tested?
local build

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #13190 from zhengruifeng/update_recd.

examples/src/main/java/org/apache/spark/examples/JavaHdfsLR.java

@@ -32,8 +32,7 @@ import java.util.regex.Pattern;
  * Logistic regression based classification.
  *
  * This is an example implementation for learning how to use Spark. For more conventional use,
- * please refer to either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
- * org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS based on your needs.
+ * please refer to org.apache.spark.ml.classification.LogisticRegression.
  */
 public final class JavaHdfsLR {
 
@@ -43,8 +42,7 @@ public final class JavaHdfsLR {
   static void showWarning() {
     String warning = "WARN: This is a naive implementation of Logistic Regression " +
             "and is given as an example!\n" +
-            "Please use either org.apache.spark.mllib.classification.LogisticRegressionWithSGD " +
-            "or org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS " +
+            "Please use org.apache.spark.ml.classification.LogisticRegression " +
             "for more conventional use.";
     System.err.println(warning);
   }

examples/src/main/python/als.py

@@ -17,7 +17,7 @@
 
 """
 This is an example implementation of ALS for learning how to use Spark. Please refer to
-ALS in pyspark.mllib.recommendation for more conventional use.
+pyspark.ml.recommendation.ALS for more conventional use.
 
 This example requires numpy (http://www.numpy.org/)
 """
@@ -59,7 +59,7 @@ if __name__ == "__main__":
     """
 
     print("""WARN: This is a naive implementation of ALS and is given as an
-      example. Please use the ALS method found in pyspark.mllib.recommendation for more
+      example. Please use pyspark.ml.recommendation.ALS for more
       conventional use.""", file=sys.stderr)
 
     sc = SparkContext(appName="PythonALS")

examples/src/main/python/kmeans.py

@@ -17,8 +17,8 @@
 
 """
 The K-means algorithm written from scratch against PySpark. In practice,
-one may prefer to use the KMeans algorithm in MLlib, as shown in
-examples/src/main/python/mllib/kmeans.py.
+one may prefer to use the KMeans algorithm in ML, as shown in
+examples/src/main/python/ml/kmeans_example.py.
 
 This example requires NumPy (http://www.numpy.org/).
 """
@@ -52,8 +52,8 @@ if __name__ == "__main__":
         exit(-1)
 
     print("""WARN: This is a naive implementation of KMeans Clustering and is given
-       as an example! Please refer to examples/src/main/python/mllib/kmeans.py for an example on
-       how to use MLlib's KMeans implementation.""", file=sys.stderr)
+       as an example! Please refer to examples/src/main/python/ml/kmeans_example.py for an
+       example on how to use ML's KMeans implementation.""", file=sys.stderr)
 
     sc = SparkContext(appName="PythonKMeans")
     lines = sc.textFile(sys.argv[1])

examples/src/main/python/logistic_regression.py

@@ -20,7 +20,7 @@ A logistic regression implementation that uses NumPy (http://www.numpy.org)
 to act on batches of input data using efficient matrix operations.
 
 In practice, one may prefer to use the LogisticRegression algorithm in
-MLlib, as shown in examples/src/main/python/mllib/logistic_regression.py.
+ML, as shown in examples/src/main/python/ml/logistic_regression_with_elastic_net.py.
 """
 from __future__ import print_function
 
@@ -51,8 +51,9 @@ if __name__ == "__main__":
         exit(-1)
 
     print("""WARN: This is a naive implementation of Logistic Regression and is
-      given as an example! Please refer to examples/src/main/python/mllib/logistic_regression.py
-      to see how MLlib's implementation is used.""", file=sys.stderr)
+      given as an example!
+      Please refer to examples/src/main/python/ml/logistic_regression_with_elastic_net.py
+      to see how ML's implementation is used.""", file=sys.stderr)
 
     sc = SparkContext(appName="PythonLR")
     points = sc.textFile(sys.argv[1]).mapPartitions(readPointBatch).cache()

examples/src/main/scala/org/apache/spark/examples/LocalALS.scala

@@ -24,7 +24,7 @@ import org.apache.commons.math3.linear._
  * Alternating least squares matrix factorization.
  *
  * This is an example implementation for learning how to use Spark. For more conventional use,
- * please refer to org.apache.spark.mllib.recommendation.ALS
+ * please refer to org.apache.spark.ml.recommendation.ALS.
  */
 object LocalALS {
 
@@ -96,7 +96,7 @@ object LocalALS {
   def showWarning() {
     System.err.println(
       """WARN: This is a naive implementation of ALS and is given as an example!
-        |Please use the ALS method found in org.apache.spark.mllib.recommendation
+        |Please use org.apache.spark.ml.recommendation.ALS
         |for more conventional use.
       """.stripMargin)
   }

examples/src/main/scala/org/apache/spark/examples/LocalFileLR.scala

@@ -26,8 +26,7 @@ import breeze.linalg.{DenseVector, Vector}
  * Logistic regression based classification.
  *
  * This is an example implementation for learning how to use Spark. For more conventional use,
- * please refer to either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
- * org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS based on your needs.
+ * please refer to org.apache.spark.ml.classification.LogisticRegression.
  */
 object LocalFileLR {
   val D = 10   // Number of dimensions
@@ -43,8 +42,7 @@ object LocalFileLR {
   def showWarning() {
     System.err.println(
       """WARN: This is a naive implementation of Logistic Regression and is given as an example!
-        |Please use either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
-        |org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS
+        |Please use org.apache.spark.ml.classification.LogisticRegression
         |for more conventional use.
       """.stripMargin)
   }

examples/src/main/scala/org/apache/spark/examples/LocalKMeans.scala

@@ -29,7 +29,7 @@ import breeze.linalg.{squaredDistance, DenseVector, Vector}
  * K-means clustering.
  *
  * This is an example implementation for learning how to use Spark. For more conventional use,
- * please refer to org.apache.spark.mllib.clustering.KMeans
+ * please refer to org.apache.spark.ml.clustering.KMeans.
  */
 object LocalKMeans {
   val N = 1000
@@ -66,7 +66,7 @@ object LocalKMeans {
   def showWarning() {
     System.err.println(
       """WARN: This is a naive implementation of KMeans Clustering and is given as an example!
-        |Please use the KMeans method found in org.apache.spark.mllib.clustering
+        |Please use org.apache.spark.ml.clustering.KMeans
         |for more conventional use.
       """.stripMargin)
   }

examples/src/main/scala/org/apache/spark/examples/LocalLR.scala

@@ -26,8 +26,7 @@ import breeze.linalg.{DenseVector, Vector}
  * Logistic regression based classification.
  *
  * This is an example implementation for learning how to use Spark. For more conventional use,
- * please refer to either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
- * org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS based on your needs.
+ * please refer to org.apache.spark.ml.classification.LogisticRegression.
  */
 object LocalLR {
   val N = 10000  // Number of data points
@@ -50,8 +49,7 @@ object LocalLR {
   def showWarning() {
     System.err.println(
       """WARN: This is a naive implementation of Logistic Regression and is given as an example!
-        |Please use either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
-        |org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS
+        |Please use org.apache.spark.ml.classification.LogisticRegression
         |for more conventional use.
       """.stripMargin)
   }

examples/src/main/scala/org/apache/spark/examples/SparkALS.scala

@@ -26,7 +26,7 @@ import org.apache.spark._
  * Alternating least squares matrix factorization.
  *
  * This is an example implementation for learning how to use Spark. For more conventional use,
- * please refer to org.apache.spark.mllib.recommendation.ALS
+ * please refer to org.apache.spark.ml.recommendation.ALS.
  */
 object SparkALS {
 
@@ -81,7 +81,7 @@ object SparkALS {
   def showWarning() {
     System.err.println(
       """WARN: This is a naive implementation of ALS and is given as an example!
-        |Please use the ALS method found in org.apache.spark.mllib.recommendation
+        |Please use org.apache.spark.ml.recommendation.ALS
         |for more conventional use.
       """.stripMargin)
   }

examples/src/main/scala/org/apache/spark/examples/SparkHdfsLR.scala

@@ -31,8 +31,7 @@ import org.apache.spark._
  * Logistic regression based classification.
  *
  * This is an example implementation for learning how to use Spark. For more conventional use,
- * please refer to either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
- * org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS based on your needs.
+ * please refer to org.apache.spark.ml.classification.LogisticRegression.
  */
 object SparkHdfsLR {
   val D = 10   // Number of dimensions
@@ -54,8 +53,7 @@ object SparkHdfsLR {
   def showWarning() {
     System.err.println(
       """WARN: This is a naive implementation of Logistic Regression and is given as an example!
-        |Please use either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
-        |org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS
+        |Please use org.apache.spark.ml.classification.LogisticRegression
         |for more conventional use.
       """.stripMargin)
   }

examples/src/main/scala/org/apache/spark/examples/SparkKMeans.scala

@@ -26,7 +26,7 @@ import org.apache.spark.{SparkConf, SparkContext}
  * K-means clustering.
  *
  * This is an example implementation for learning how to use Spark. For more conventional use,
- * please refer to org.apache.spark.mllib.clustering.KMeans
+ * please refer to org.apache.spark.ml.clustering.KMeans.
  */
 object SparkKMeans {
 
@@ -52,7 +52,7 @@ object SparkKMeans {
   def showWarning() {
     System.err.println(
       """WARN: This is a naive implementation of KMeans Clustering and is given as an example!
-        |Please use the KMeans method found in org.apache.spark.mllib.clustering
+        |Please use org.apache.spark.ml.clustering.KMeans
         |for more conventional use.
       """.stripMargin)
   }

examples/src/main/scala/org/apache/spark/examples/SparkLR.scala

@@ -31,8 +31,7 @@ import org.apache.spark._
  * Usage: SparkLR [slices]
  *
  * This is an example implementation for learning how to use Spark. For more conventional use,
- * please refer to either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
- * org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS based on your needs.
+ * please refer to org.apache.spark.ml.classification.LogisticRegression.
  */
 object SparkLR {
   val N = 10000  // Number of data points
@@ -55,8 +54,7 @@ object SparkLR {
   def showWarning() {
     System.err.println(
       """WARN: This is a naive implementation of Logistic Regression and is given as an example!
-        |Please use either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
-        |org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS
+        |Please use org.apache.spark.ml.classification.LogisticRegression
         |for more conventional use.
       """.stripMargin)
   }