addressed comments

Author: brkyvz

mllib/src/main/scala/org/apache/spark/ml/param/params.scala

@@ -220,19 +220,15 @@ class BooleanParam(parent: Params, name: String, doc: String) // No need for isV
 }
 
 /** Specialized version of [[Param[Array[T]]]] for Java. */
-class ArrayParam[T : ClassTag](
-    parent: Params,
-    name: String,
-    doc: String,
-    isValid: Array[T] => Boolean)
-  extends Param[Array[T]](parent, name, doc, isValid) {
+class StringArrayParam(parent: Params, name: String, doc: String, isValid: Array[String] => Boolean)
+  extends Param[Array[String]](parent, name, doc, isValid) {
 
   def this(parent: Params, name: String, doc: String) =
     this(parent, name, doc, ParamValidators.alwaysTrue)
 
-  override def w(value: Array[T]): ParamPair[Array[T]] = super.w(value)
+  override def w(value: Array[String]): ParamPair[Array[String]] = super.w(value)
 
-  private[param] def wCast(value: Seq[T]): ParamPair[Array[T]] = w(value.toArray)
+  private[param] def wCast(value: Seq[String]): ParamPair[Array[String]] = w(value.toArray)
 }
 
 /**
@@ -328,8 +324,8 @@ trait Params extends Identifiable with Serializable {
    */
   protected final def set[T](param: Param[T], value: T): this.type = {
     shouldOwn(param)
-    if (param.isInstanceOf[ArrayParam[_]] && value.isInstanceOf[Seq[_]]) {
-      paramMap.put(param.asInstanceOf[ArrayParam[Any]].wCast(value.asInstanceOf[Seq[Any]]))
+    if (param.isInstanceOf[StringArrayParam] && value.isInstanceOf[Seq[_]]) {
+      paramMap.put(param.asInstanceOf[StringArrayParam].wCast(value.asInstanceOf[Seq[String]]))
     } else {
       paramMap.put(param.w(value))
     }

mllib/src/main/scala/org/apache/spark/ml/param/shared/SharedParamsCodeGen.scala

@@ -83,7 +83,7 @@ private[shared] object SharedParamsCodeGen {
         case _ if c == classOf[Float] => "FloatParam"
         case _ if c == classOf[Double] => "DoubleParam"
         case _ if c == classOf[Boolean] => "BooleanParam"
-        case _ if c.isArray => s"ArrayParam[${getTypeString(c.getComponentType)}]"
+        case _ if c.isArray && c.getComponentType == classOf[String] => s"StringArrayParam"
         case _ => s"Param[${getTypeString(c)}]"
       }
     }

mllib/src/main/scala/org/apache/spark/ml/param/shared/sharedParams.scala

@@ -178,7 +178,7 @@ private[ml] trait HasInputCols extends Params {
    * Param for input column names.
    * @group param
    */
-  final val inputCols: ArrayParam[String] = new ArrayParam[String](this, "inputCols", "input column names")
+  final val inputCols: StringArrayParam = new StringArrayParam(this, "inputCols", "input column names")
 
   /** @group getParam */
   final def getInputCols: Array[String] = $(inputCols)