[SPARK-18592][ML] Move DT/RF/GBT Param setter methods to subclasses

## What changes were proposed in this pull request?
Mainly two changes:
* Move DT/RF/GBT Param setter methods to subclasses.
* Deprecate corresponding setter methods in the model classes.

See discussion here https://github.com/apache/spark/pull/15913#discussion_r89662469.

## How was this patch tested?
Existing tests.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #16017 from yanboliang/spark-18592.

mllib/src/main/scala/org/apache/spark/ml/classification/DecisionTreeClassifier.scala

@@ -52,33 +52,49 @@ class DecisionTreeClassifier @Since("1.4.0") (
 
   // Override parameter setters from parent trait for Java API compatibility.
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMaxDepth(value: Int): this.type = super.setMaxDepth(value)
+  override def setMaxDepth(value: Int): this.type = set(maxDepth, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMaxBins(value: Int): this.type = super.setMaxBins(value)
+  override def setMaxBins(value: Int): this.type = set(maxBins, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMinInstancesPerNode(value: Int): this.type =
-    super.setMinInstancesPerNode(value)
+  override def setMinInstancesPerNode(value: Int): this.type = set(minInstancesPerNode, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMinInfoGain(value: Double): this.type = super.setMinInfoGain(value)
+  override def setMinInfoGain(value: Double): this.type = set(minInfoGain, value)
 
+  /** @group expertSetParam */
   @Since("1.4.0")
-  override def setMaxMemoryInMB(value: Int): this.type = super.setMaxMemoryInMB(value)
+  override def setMaxMemoryInMB(value: Int): this.type = set(maxMemoryInMB, value)
 
+  /** @group expertSetParam */
   @Since("1.4.0")
-  override def setCacheNodeIds(value: Boolean): this.type = super.setCacheNodeIds(value)
+  override def setCacheNodeIds(value: Boolean): this.type = set(cacheNodeIds, value)
 
+  /**
+   * Specifies how often to checkpoint the cached node IDs.
+   * E.g. 10 means that the cache will get checkpointed every 10 iterations.
+   * This is only used if cacheNodeIds is true and if the checkpoint directory is set in
+   * [[org.apache.spark.SparkContext]].
+   * Must be >= 1.
+   * (default = 10)
+   * @group setParam
+   */
   @Since("1.4.0")
-  override def setCheckpointInterval(value: Int): this.type = super.setCheckpointInterval(value)
+  override def setCheckpointInterval(value: Int): this.type = set(checkpointInterval, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setImpurity(value: String): this.type = super.setImpurity(value)
+  override def setImpurity(value: String): this.type = set(impurity, value)
 
+  /** @group setParam */
   @Since("1.6.0")
-  override def setSeed(value: Long): this.type = super.setSeed(value)
+  override def setSeed(value: Long): this.type = set(seed, value)
 
   override protected def train(dataset: Dataset[_]): DecisionTreeClassificationModel = {
     val categoricalFeatures: Map[Int, Int] =

mllib/src/main/scala/org/apache/spark/ml/classification/GBTClassifier.scala

@@ -69,31 +69,47 @@ class GBTClassifier @Since("1.4.0") (
 
   // Parameters from TreeClassifierParams:
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMaxDepth(value: Int): this.type = super.setMaxDepth(value)
+  override def setMaxDepth(value: Int): this.type = set(maxDepth, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMaxBins(value: Int): this.type = super.setMaxBins(value)
+  override def setMaxBins(value: Int): this.type = set(maxBins, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMinInstancesPerNode(value: Int): this.type =
-    super.setMinInstancesPerNode(value)
+  override def setMinInstancesPerNode(value: Int): this.type = set(minInstancesPerNode, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMinInfoGain(value: Double): this.type = super.setMinInfoGain(value)
+  override def setMinInfoGain(value: Double): this.type = set(minInfoGain, value)
 
+  /** @group expertSetParam */
   @Since("1.4.0")
-  override def setMaxMemoryInMB(value: Int): this.type = super.setMaxMemoryInMB(value)
+  override def setMaxMemoryInMB(value: Int): this.type = set(maxMemoryInMB, value)
 
+  /** @group expertSetParam */
   @Since("1.4.0")
-  override def setCacheNodeIds(value: Boolean): this.type = super.setCacheNodeIds(value)
+  override def setCacheNodeIds(value: Boolean): this.type = set(cacheNodeIds, value)
 
+  /**
+   * Specifies how often to checkpoint the cached node IDs.
+   * E.g. 10 means that the cache will get checkpointed every 10 iterations.
+   * This is only used if cacheNodeIds is true and if the checkpoint directory is set in
+   * [[org.apache.spark.SparkContext]].
+   * Must be >= 1.
+   * (default = 10)
+   * @group setParam
+   */
   @Since("1.4.0")
-  override def setCheckpointInterval(value: Int): this.type = super.setCheckpointInterval(value)
+  override def setCheckpointInterval(value: Int): this.type = set(checkpointInterval, value)
 
   /**
    * The impurity setting is ignored for GBT models.
    * Individual trees are built using impurity "Variance."
+   *
+   * @group setParam
    */
   @Since("1.4.0")
   override def setImpurity(value: String): this.type = {
@@ -103,19 +119,23 @@ class GBTClassifier @Since("1.4.0") (
 
   // Parameters from TreeEnsembleParams:
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setSubsamplingRate(value: Double): this.type = super.setSubsamplingRate(value)
+  override def setSubsamplingRate(value: Double): this.type = set(subsamplingRate, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setSeed(value: Long): this.type = super.setSeed(value)
+  override def setSeed(value: Long): this.type = set(seed, value)
 
   // Parameters from GBTParams:
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMaxIter(value: Int): this.type = super.setMaxIter(value)
+  override def setMaxIter(value: Int): this.type = set(maxIter, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setStepSize(value: Double): this.type = super.setStepSize(value)
+  override def setStepSize(value: Double): this.type = set(stepSize, value)
 
   // Parameters from GBTClassifierParams:
 

mllib/src/main/scala/org/apache/spark/ml/classification/RandomForestClassifier.scala

@@ -54,47 +54,66 @@ class RandomForestClassifier @Since("1.4.0") (
 
   // Parameters from TreeClassifierParams:
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMaxDepth(value: Int): this.type = super.setMaxDepth(value)
+  override def setMaxDepth(value: Int): this.type = set(maxDepth, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMaxBins(value: Int): this.type = super.setMaxBins(value)
+  override def setMaxBins(value: Int): this.type = set(maxBins, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMinInstancesPerNode(value: Int): this.type =
-    super.setMinInstancesPerNode(value)
+  override def setMinInstancesPerNode(value: Int): this.type = set(minInstancesPerNode, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMinInfoGain(value: Double): this.type = super.setMinInfoGain(value)
+  override def setMinInfoGain(value: Double): this.type = set(minInfoGain, value)
 
+  /** @group expertSetParam */
   @Since("1.4.0")
-  override def setMaxMemoryInMB(value: Int): this.type = super.setMaxMemoryInMB(value)
+  override def setMaxMemoryInMB(value: Int): this.type = set(maxMemoryInMB, value)
 
+  /** @group expertSetParam */
   @Since("1.4.0")
-  override def setCacheNodeIds(value: Boolean): this.type = super.setCacheNodeIds(value)
+  override def setCacheNodeIds(value: Boolean): this.type = set(cacheNodeIds, value)
 
+  /**
+   * Specifies how often to checkpoint the cached node IDs.
+   * E.g. 10 means that the cache will get checkpointed every 10 iterations.
+   * This is only used if cacheNodeIds is true and if the checkpoint directory is set in
+   * [[org.apache.spark.SparkContext]].
+   * Must be >= 1.
+   * (default = 10)
+   * @group setParam
+   */
   @Since("1.4.0")
-  override def setCheckpointInterval(value: Int): this.type = super.setCheckpointInterval(value)
+  override def setCheckpointInterval(value: Int): this.type = set(checkpointInterval, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setImpurity(value: String): this.type = super.setImpurity(value)
+  override def setImpurity(value: String): this.type = set(impurity, value)
 
   // Parameters from TreeEnsembleParams:
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setSubsamplingRate(value: Double): this.type = super.setSubsamplingRate(value)
+  override def setSubsamplingRate(value: Double): this.type = set(subsamplingRate, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setSeed(value: Long): this.type = super.setSeed(value)
+  override def setSeed(value: Long): this.type = set(seed, value)
 
   // Parameters from RandomForestParams:
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setNumTrees(value: Int): this.type = super.setNumTrees(value)
+  override def setNumTrees(value: Int): this.type = set(numTrees, value)
 
+  /** @group setParam */
   @Since("1.4.0")
   override def setFeatureSubsetStrategy(value: String): this.type =
-    super.setFeatureSubsetStrategy(value)
+    set(featureSubsetStrategy, value)
 
   override protected def train(dataset: Dataset[_]): RandomForestClassificationModel = {
     val categoricalFeatures: Map[Int, Int] =

mllib/src/main/scala/org/apache/spark/ml/regression/DecisionTreeRegressor.scala

@@ -51,34 +51,52 @@ class DecisionTreeRegressor @Since("1.4.0") (@Since("1.4.0") override val uid: S
   def this() = this(Identifiable.randomUID("dtr"))
 
   // Override parameter setters from parent trait for Java API compatibility.
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMaxDepth(value: Int): this.type = super.setMaxDepth(value)
+  override def setMaxDepth(value: Int): this.type = set(maxDepth, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMaxBins(value: Int): this.type = super.setMaxBins(value)
+  override def setMaxBins(value: Int): this.type = set(maxBins, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMinInstancesPerNode(value: Int): this.type =
-    super.setMinInstancesPerNode(value)
+  override def setMinInstancesPerNode(value: Int): this.type = set(minInstancesPerNode, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMinInfoGain(value: Double): this.type = super.setMinInfoGain(value)
+  override def setMinInfoGain(value: Double): this.type = set(minInfoGain, value)
 
+  /** @group expertSetParam */
   @Since("1.4.0")
-  override def setMaxMemoryInMB(value: Int): this.type = super.setMaxMemoryInMB(value)
+  override def setMaxMemoryInMB(value: Int): this.type = set(maxMemoryInMB, value)
 
+  /** @group expertSetParam */
   @Since("1.4.0")
-  override def setCacheNodeIds(value: Boolean): this.type = super.setCacheNodeIds(value)
+  override def setCacheNodeIds(value: Boolean): this.type = set(cacheNodeIds, value)
 
+  /**
+   * Specifies how often to checkpoint the cached node IDs.
+   * E.g. 10 means that the cache will get checkpointed every 10 iterations.
+   * This is only used if cacheNodeIds is true and if the checkpoint directory is set in
+   * [[org.apache.spark.SparkContext]].
+   * Must be >= 1.
+   * (default = 10)
+   * @group setParam
+   */
   @Since("1.4.0")
-  override def setCheckpointInterval(value: Int): this.type = super.setCheckpointInterval(value)
+  override def setCheckpointInterval(value: Int): this.type = set(checkpointInterval, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setImpurity(value: String): this.type = super.setImpurity(value)
+  override def setImpurity(value: String): this.type = set(impurity, value)
 
-  override def setSeed(value: Long): this.type = super.setSeed(value)
+  /** @group setParam */
+  @Since("1.6.0")
+  override def setSeed(value: Long): this.type = set(seed, value)
 
   /** @group setParam */
+  @Since("2.0.0")
   def setVarianceCol(value: String): this.type = set(varianceCol, value)
 
   override protected def train(dataset: Dataset[_]): DecisionTreeRegressionModel = {

mllib/src/main/scala/org/apache/spark/ml/regression/GBTRegressor.scala

@@ -65,31 +65,48 @@ class GBTRegressor @Since("1.4.0") (@Since("1.4.0") override val uid: String)
   // Override parameter setters from parent trait for Java API compatibility.
 
   // Parameters from TreeRegressorParams:
+
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMaxDepth(value: Int): this.type = super.setMaxDepth(value)
+  override def setMaxDepth(value: Int): this.type = set(maxDepth, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMaxBins(value: Int): this.type = super.setMaxBins(value)
+  override def setMaxBins(value: Int): this.type = set(maxBins, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMinInstancesPerNode(value: Int): this.type =
-    super.setMinInstancesPerNode(value)
+  override def setMinInstancesPerNode(value: Int): this.type = set(minInstancesPerNode, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMinInfoGain(value: Double): this.type = super.setMinInfoGain(value)
+  override def setMinInfoGain(value: Double): this.type = set(minInfoGain, value)
 
+  /** @group expertSetParam */
   @Since("1.4.0")
-  override def setMaxMemoryInMB(value: Int): this.type = super.setMaxMemoryInMB(value)
+  override def setMaxMemoryInMB(value: Int): this.type = set(maxMemoryInMB, value)
 
+  /** @group expertSetParam */
   @Since("1.4.0")
-  override def setCacheNodeIds(value: Boolean): this.type = super.setCacheNodeIds(value)
+  override def setCacheNodeIds(value: Boolean): this.type = set(cacheNodeIds, value)
 
+  /**
+   * Specifies how often to checkpoint the cached node IDs.
+   * E.g. 10 means that the cache will get checkpointed every 10 iterations.
+   * This is only used if cacheNodeIds is true and if the checkpoint directory is set in
+   * [[org.apache.spark.SparkContext]].
+   * Must be >= 1.
+   * (default = 10)
+   * @group setParam
+   */
   @Since("1.4.0")
-  override def setCheckpointInterval(value: Int): this.type = super.setCheckpointInterval(value)
+  override def setCheckpointInterval(value: Int): this.type = set(checkpointInterval, value)
 
   /**
    * The impurity setting is ignored for GBT models.
    * Individual trees are built using impurity "Variance."
+   *
+   * @group setParam
    */
   @Since("1.4.0")
   override def setImpurity(value: String): this.type = {
@@ -98,18 +115,24 @@ class GBTRegressor @Since("1.4.0") (@Since("1.4.0") override val uid: String)
   }
 
   // Parameters from TreeEnsembleParams:
+
+  /** @group setParam */
   @Since("1.4.0")
-  override def setSubsamplingRate(value: Double): this.type = super.setSubsamplingRate(value)
+  override def setSubsamplingRate(value: Double): this.type = set(subsamplingRate, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setSeed(value: Long): this.type = super.setSeed(value)
+  override def setSeed(value: Long): this.type = set(seed, value)
 
   // Parameters from GBTParams:
+
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMaxIter(value: Int): this.type = super.setMaxIter(value)
+  override def setMaxIter(value: Int): this.type = set(maxIter, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setStepSize(value: Double): this.type = super.setStepSize(value)
+  override def setStepSize(value: Double): this.type = set(stepSize, value)
 
   // Parameters from GBTRegressorParams:
 

mllib/src/main/scala/org/apache/spark/ml/regression/RandomForestRegressor.scala

@@ -52,45 +52,67 @@ class RandomForestRegressor @Since("1.4.0") (@Since("1.4.0") override val uid: S
   // Override parameter setters from parent trait for Java API compatibility.
 
   // Parameters from TreeRegressorParams:
+
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMaxDepth(value: Int): this.type = super.setMaxDepth(value)
+  override def setMaxDepth(value: Int): this.type = set(maxDepth, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMaxBins(value: Int): this.type = super.setMaxBins(value)
+  override def setMaxBins(value: Int): this.type = set(maxBins, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMinInstancesPerNode(value: Int): this.type =
-    super.setMinInstancesPerNode(value)
+  override def setMinInstancesPerNode(value: Int): this.type = set(minInstancesPerNode, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setMinInfoGain(value: Double): this.type = super.setMinInfoGain(value)
+  override def setMinInfoGain(value: Double): this.type = set(minInfoGain, value)
 
+  /** @group expertSetParam */
   @Since("1.4.0")
-  override def setMaxMemoryInMB(value: Int): this.type = super.setMaxMemoryInMB(value)
+  override def setMaxMemoryInMB(value: Int): this.type = set(maxMemoryInMB, value)
 
+  /** @group expertSetParam */
   @Since("1.4.0")
-  override def setCacheNodeIds(value: Boolean): this.type = super.setCacheNodeIds(value)
+  override def setCacheNodeIds(value: Boolean): this.type = set(cacheNodeIds, value)
 
+  /**
+   * Specifies how often to checkpoint the cached node IDs.
+   * E.g. 10 means that the cache will get checkpointed every 10 iterations.
+   * This is only used if cacheNodeIds is true and if the checkpoint directory is set in
+   * [[org.apache.spark.SparkContext]].
+   * Must be >= 1.
+   * (default = 10)
+   * @group setParam
+   */
   @Since("1.4.0")
-  override def setCheckpointInterval(value: Int): this.type = super.setCheckpointInterval(value)
+  override def setCheckpointInterval(value: Int): this.type = set(checkpointInterval, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setImpurity(value: String): this.type = super.setImpurity(value)
+  override def setImpurity(value: String): this.type = set(impurity, value)
 
   // Parameters from TreeEnsembleParams:
+
+  /** @group setParam */
   @Since("1.4.0")
-  override def setSubsamplingRate(value: Double): this.type = super.setSubsamplingRate(value)
+  override def setSubsamplingRate(value: Double): this.type = set(subsamplingRate, value)
 
+  /** @group setParam */
   @Since("1.4.0")
-  override def setSeed(value: Long): this.type = super.setSeed(value)
+  override def setSeed(value: Long): this.type = set(seed, value)
 
   // Parameters from RandomForestParams:
+
+  /** @group setParam */
   @Since("1.4.0")
-  override def setNumTrees(value: Int): this.type = super.setNumTrees(value)
+  override def setNumTrees(value: Int): this.type = set(numTrees, value)
 
+  /** @group setParam */
   @Since("1.4.0")
   override def setFeatureSubsetStrategy(value: String): this.type =
-    super.setFeatureSubsetStrategy(value)
+    set(featureSubsetStrategy, value)
 
   override protected def train(dataset: Dataset[_]): RandomForestRegressionModel = {
     val categoricalFeatures: Map[Int, Int] =

mllib/src/main/scala/org/apache/spark/ml/tree/treeParams.scala

@@ -107,54 +107,78 @@ private[ml] trait DecisionTreeParams extends PredictorParams
   setDefault(maxDepth -> 5, maxBins -> 32, minInstancesPerNode -> 1, minInfoGain -> 0.0,
     maxMemoryInMB -> 256, cacheNodeIds -> false, checkpointInterval -> 10)
 
-  /** @group setParam */
+  /**
+   * @deprecated This method is deprecated and will be removed in 2.2.0.
+   * @group setParam
+   */
+  @deprecated("This method is deprecated and will be removed in 2.2.0.", "2.1.0")
   def setMaxDepth(value: Int): this.type = set(maxDepth, value)
 
   /** @group getParam */
   final def getMaxDepth: Int = $(maxDepth)
 
-  /** @group setParam */
+  /**
+   * @deprecated This method is deprecated and will be removed in 2.2.0.
+   * @group setParam
+   */
+  @deprecated("This method is deprecated and will be removed in 2.2.0.", "2.1.0")
   def setMaxBins(value: Int): this.type = set(maxBins, value)
 
   /** @group getParam */
   final def getMaxBins: Int = $(maxBins)
 
-  /** @group setParam */
+  /**
+   * @deprecated This method is deprecated and will be removed in 2.2.0.
+   * @group setParam
+   */
+  @deprecated("This method is deprecated and will be removed in 2.2.0.", "2.1.0")
   def setMinInstancesPerNode(value: Int): this.type = set(minInstancesPerNode, value)
 
   /** @group getParam */
   final def getMinInstancesPerNode: Int = $(minInstancesPerNode)
 
-  /** @group setParam */
+  /**
+   * @deprecated This method is deprecated and will be removed in 2.2.0.
+   * @group setParam
+   */
+  @deprecated("This method is deprecated and will be removed in 2.2.0.", "2.1.0")
   def setMinInfoGain(value: Double): this.type = set(minInfoGain, value)
 
   /** @group getParam */
   final def getMinInfoGain: Double = $(minInfoGain)
 
-  /** @group setParam */
+  /**
+   * @deprecated This method is deprecated and will be removed in 2.2.0.
+   * @group setParam
+   */
+  @deprecated("This method is deprecated and will be removed in 2.2.0.", "2.1.0")
   def setSeed(value: Long): this.type = set(seed, value)
 
-  /** @group expertSetParam */
+  /**
+   * @deprecated This method is deprecated and will be removed in 2.2.0.
+   * @group expertSetParam
+   */
+  @deprecated("This method is deprecated and will be removed in 2.2.0.", "2.1.0")
   def setMaxMemoryInMB(value: Int): this.type = set(maxMemoryInMB, value)
 
   /** @group expertGetParam */
   final def getMaxMemoryInMB: Int = $(maxMemoryInMB)
 
-  /** @group expertSetParam */
+  /**
+   * @deprecated This method is deprecated and will be removed in 2.2.0.
+   * @group expertSetParam
+   */
+  @deprecated("This method is deprecated and will be removed in 2.2.0.", "2.1.0")
   def setCacheNodeIds(value: Boolean): this.type = set(cacheNodeIds, value)
 
   /** @group expertGetParam */
   final def getCacheNodeIds: Boolean = $(cacheNodeIds)
 
   /**
-   * Specifies how often to checkpoint the cached node IDs.
-   * E.g. 10 means that the cache will get checkpointed every 10 iterations.
-   * This is only used if cacheNodeIds is true and if the checkpoint directory is set in
-   * [[org.apache.spark.SparkContext]].
-   * Must be >= 1.
-   * (default = 10)
+   * @deprecated This method is deprecated and will be removed in 2.2.0.
    * @group setParam
    */
+  @deprecated("This method is deprecated and will be removed in 2.2.0.", "2.1.0")
   def setCheckpointInterval(value: Int): this.type = set(checkpointInterval, value)
 
   /** (private[ml]) Create a Strategy instance to use with the old API. */
@@ -198,7 +222,11 @@ private[ml] trait TreeClassifierParams extends Params {
 
   setDefault(impurity -> "gini")
 
-  /** @group setParam */
+  /**
+   * @deprecated This method is deprecated and will be removed in 2.2.0.
+   * @group setParam
+   */
+  @deprecated("This method is deprecated and will be removed in 2.2.0.", "2.1.0")
   def setImpurity(value: String): this.type = set(impurity, value)
 
   /** @group getParam */
@@ -243,7 +271,11 @@ private[ml] trait TreeRegressorParams extends Params {
 
   setDefault(impurity -> "variance")
 
-  /** @group setParam */
+  /**
+   * @deprecated This method is deprecated and will be removed in 2.2.0.
+   * @group setParam
+   */
+  @deprecated("This method is deprecated and will be removed in 2.2.0.", "2.1.0")
   def setImpurity(value: String): this.type = set(impurity, value)
 
   /** @group getParam */
@@ -300,7 +332,11 @@ private[ml] trait TreeEnsembleParams extends DecisionTreeParams {
 
   setDefault(subsamplingRate -> 1.0)
 
-  /** @group setParam */
+  /**
+   * @deprecated This method is deprecated and will be removed in 2.2.0.
+   * @group setParam
+   */
+  @deprecated("This method is deprecated and will be removed in 2.2.0.", "2.1.0")
   def setSubsamplingRate(value: Double): this.type = set(subsamplingRate, value)
 
   /** @group getParam */
@@ -340,7 +376,11 @@ private[ml] trait RandomForestParams extends TreeEnsembleParams {
 
   setDefault(numTrees -> 20)
 
-  /** @group setParam */
+  /**
+   * @deprecated This method is deprecated and will be removed in 2.2.0.
+   * @group setParam
+   */
+  @deprecated("This method is deprecated and will be removed in 2.2.0.", "2.1.0")
   def setNumTrees(value: Int): this.type = set(numTrees, value)
 
   /** @group getParam */
@@ -383,7 +423,11 @@ private[ml] trait RandomForestParams extends TreeEnsembleParams {
 
   setDefault(featureSubsetStrategy -> "auto")
 
-  /** @group setParam */
+  /**
+   * @deprecated This method is deprecated and will be removed in 2.2.0.
+   * @group setParam
+   */
+  @deprecated("This method is deprecated and will be removed in 2.2.0.", "2.1.0")
   def setFeatureSubsetStrategy(value: String): this.type = set(featureSubsetStrategy, value)
 
   /** @group getParam */
@@ -420,7 +464,11 @@ private[ml] trait GBTParams extends TreeEnsembleParams with HasMaxIter {
   // final val validationTol: DoubleParam = new DoubleParam(this, "validationTol", "")
   // validationTol -> 1e-5
 
-  /** @group setParam */
+  /**
+   * @deprecated This method is deprecated and will be removed in 2.2.0.
+   * @group setParam
+   */
+  @deprecated("This method is deprecated and will be removed in 2.2.0.", "2.1.0")
   def setMaxIter(value: Int): this.type = set(maxIter, value)
 
   /**
@@ -436,7 +484,11 @@ private[ml] trait GBTParams extends TreeEnsembleParams with HasMaxIter {
   /** @group getParam */
   final def getStepSize: Double = $(stepSize)
 
-  /** @group setParam */
+  /**
+   * @deprecated This method is deprecated and will be removed in 2.2.0.
+   * @group setParam
+   */
+  @deprecated("This method is deprecated and will be removed in 2.2.0.", "2.1.0")
   def setStepSize(value: Double): this.type = set(stepSize, value)
 
   setDefault(maxIter -> 20, stepSize -> 0.1)