diff --git a/mllib/src/main/scala/org/apache/spark/ml/tree/impl/DecisionTreeMetadata.scala b/mllib/src/main/scala/org/apache/spark/ml/tree/impl/DecisionTreeMetadata.scala
index c7cde1563fc79..5f7c40f6071f6 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/tree/impl/DecisionTreeMetadata.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/tree/impl/DecisionTreeMetadata.scala
@@ -18,8 +18,10 @@
 package org.apache.spark.ml.tree.impl
 
 import scala.collection.mutable
+import scala.util.Try
 
 import org.apache.spark.internal.Logging
+import org.apache.spark.ml.tree.RandomForestParams
 import org.apache.spark.mllib.regression.LabeledPoint
 import org.apache.spark.mllib.tree.configuration.Algo._
 import org.apache.spark.mllib.tree.configuration.QuantileStrategy._
@@ -184,15 +186,22 @@ private[spark] object DecisionTreeMetadata extends Logging {
       case _ => featureSubsetStrategy
     }
 
-    val isIntRegex = "^([1-9]\\d*)$".r
-    val isFractionRegex = "^(0?\\.\\d*[1-9]\\d*|1\\.0+)$".r
     val numFeaturesPerNode: Int = _featureSubsetStrategy match {
       case "all" => numFeatures
       case "sqrt" => math.sqrt(numFeatures).ceil.toInt
       case "log2" => math.max(1, (math.log(numFeatures) / math.log(2)).ceil.toInt)
       case "onethird" => (numFeatures / 3.0).ceil.toInt
-      case isIntRegex(number) => if (BigInt(number) > numFeatures) numFeatures else number.toInt
-      case isFractionRegex(fraction) => (fraction.toDouble * numFeatures).ceil.toInt
+      case _ =>
+        Try(_featureSubsetStrategy.toInt).filter(_ > 0).toOption match {
+          case Some(value) => math.min(value, numFeatures)
+          case None =>
+            Try(_featureSubsetStrategy.toDouble).filter(_ > 0).filter(_ <= 1.0).toOption match {
+              case Some(value) => math.ceil(value * numFeatures).toInt
+              case _ => throw new IllegalArgumentException(s"Supported values:" +
+                s" ${RandomForestParams.supportedFeatureSubsetStrategies.mkString(", ")}," +
+                s" (0.0-1.0], [1-n].")
+            }
+        }
     }
 
     new DecisionTreeMetadata(numFeatures, numExamples, numClasses, numBins.max,
diff --git a/mllib/src/main/scala/org/apache/spark/ml/tree/treeParams.scala b/mllib/src/main/scala/org/apache/spark/ml/tree/treeParams.scala
index 0767dc17e5562..55e12acc1c51e 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/tree/treeParams.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/tree/treeParams.scala
@@ -17,6 +17,8 @@
 
 package org.apache.spark.ml.tree
 
+import scala.util.Try
+
 import org.apache.spark.ml.PredictorParams
 import org.apache.spark.ml.param._
 import org.apache.spark.ml.param.shared._
@@ -346,10 +348,12 @@ private[ml] trait HasFeatureSubsetStrategy extends Params {
    */
   final val featureSubsetStrategy: Param[String] = new Param[String](this, "featureSubsetStrategy",
     "The number of features to consider for splits at each tree node." +
-      s" Supported options: ${RandomForestParams.supportedFeatureSubsetStrategies.mkString(", ")}",
+      s" Supported options: ${RandomForestParams.supportedFeatureSubsetStrategies.mkString(", ")}" +
+      s", (0.0-1.0], [1-n].",
     (value: String) =>
       RandomForestParams.supportedFeatureSubsetStrategies.contains(value.toLowerCase)
-      || value.matches(RandomForestParams.supportedFeatureSubsetStrategiesRegex))
+      || Try(value.toInt).filter(_ > 0).isSuccess
+      || Try(value.toDouble).filter(_ > 0).filter(_ <= 1.0).isSuccess)
 
   setDefault(featureSubsetStrategy -> "auto")
 
@@ -396,9 +400,6 @@ private[spark] object RandomForestParams {
   // These options should be lowercase.
   final val supportedFeatureSubsetStrategies: Array[String] =
     Array("auto", "all", "onethird", "sqrt", "log2").map(_.toLowerCase)
-
-  // The regex to capture "(0.0-1.0]", and "n" for integer 0 < n <= (number of features)
-  final val supportedFeatureSubsetStrategiesRegex = "^(?:[1-9]\\d*|0?\\.\\d*[1-9]\\d*|1\\.0+)$"
 }
 
 private[ml] trait RandomForestClassifierParams
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/tree/RandomForest.scala b/mllib/src/main/scala/org/apache/spark/mllib/tree/RandomForest.scala
index 26755849ad1a2..ca7fb7f51c3fc 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/tree/RandomForest.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/tree/RandomForest.scala
@@ -18,6 +18,7 @@
 package org.apache.spark.mllib.tree
 
 import scala.collection.JavaConverters._
+import scala.util.Try
 
 import org.apache.spark.annotation.Since
 import org.apache.spark.api.java.JavaRDD
@@ -76,9 +77,10 @@ private class RandomForest (
   strategy.assertValid()
   require(numTrees > 0, s"RandomForest requires numTrees > 0, but was given numTrees = $numTrees.")
   require(RandomForest.supportedFeatureSubsetStrategies.contains(featureSubsetStrategy)
-    || featureSubsetStrategy.matches(NewRFParams.supportedFeatureSubsetStrategiesRegex),
+    || Try(featureSubsetStrategy.toInt).filter(_ > 0).isSuccess
+    || Try(featureSubsetStrategy.toDouble).filter(_ > 0).filter(_ <= 1.0).isSuccess,
     s"RandomForest given invalid featureSubsetStrategy: $featureSubsetStrategy." +
-    s" Supported values: ${RandomForest.supportedFeatureSubsetStrategies.mkString(", ")}," +
+    s" Supported values: ${NewRFParams.supportedFeatureSubsetStrategies.mkString(", ")}," +
     s" (0.0-1.0], [1-n].")
 
   /**
diff --git a/mllib/src/test/scala/org/apache/spark/ml/tree/impl/RandomForestSuite.scala b/mllib/src/test/scala/org/apache/spark/ml/tree/impl/RandomForestSuite.scala
index 6db9ce150d930..1719f9fab5345 100644
--- a/mllib/src/test/scala/org/apache/spark/ml/tree/impl/RandomForestSuite.scala
+++ b/mllib/src/test/scala/org/apache/spark/ml/tree/impl/RandomForestSuite.scala
@@ -440,7 +440,7 @@ class RandomForestSuite extends SparkFunSuite with MLlibTestSparkContext {
 
     val invalidStrategies = Array("-.1", "-.10", "-0.10", ".0", "0.0", "1.1", "0")
     for (invalidStrategy <- invalidStrategies) {
-      intercept[MatchError]{
+      intercept[IllegalArgumentException]{
         val metadata =
           DecisionTreeMetadata.buildMetadata(rdd, strategy, numTrees = 1, invalidStrategy)
       }
@@ -463,7 +463,7 @@ class RandomForestSuite extends SparkFunSuite with MLlibTestSparkContext {
       checkFeatureSubsetStrategy(numTrees = 2, strategy, expected)
     }
     for (invalidStrategy <- invalidStrategies) {
-      intercept[MatchError]{
+      intercept[IllegalArgumentException]{
         val metadata =
           DecisionTreeMetadata.buildMetadata(rdd, strategy, numTrees = 2, invalidStrategy)
       }