[SPARK-6429] Implement hashCode and equals together

## What changes were proposed in this pull request?

Implement some `hashCode` and `equals` together in order to enable the scalastyle.
This is a first batch, I will continue to implement them but I wanted to know your thoughts.

Author: Joan <joan@goyeau.com>

Closes #12157 from joan38/SPARK-6429-HashCode-Equals.

3 files changed, 22 insertions, 6 deletions

diff --git a/mllib/src/main/scala/org/apache/spark/ml/tree/Split.scala b/mllib/src/main/scala/org/apache/spark/ml/tree/Split.scala
index 9d895b8fac..5d11ed0971 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/tree/Split.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/tree/Split.scala
@@ -17,6 +17,8 @@
 
 package org.apache.spark.ml.tree
 
+import java.util.Objects
+
 import org.apache.spark.annotation.{DeveloperApi, Since}
 import org.apache.spark.mllib.linalg.Vector
 import org.apache.spark.mllib.tree.configuration.{FeatureType => OldFeatureType}
@@ -112,12 +114,15 @@ final class CategoricalSplit private[ml] (
     }
   }
 
-  override def equals(o: Any): Boolean = {
-    o match {
-      case other: CategoricalSplit => featureIndex == other.featureIndex &&
-        isLeft == other.isLeft && categories == other.categories
-      case _ => false
-    }
+  override def hashCode(): Int = {
+    val state = Seq(featureIndex, isLeft, categories)
+    state.map(Objects.hashCode).foldLeft(0)((a, b) => 31 * a + b)
+  }
+
+  override def equals(o: Any): Boolean = o match {
+    case other: CategoricalSplit => featureIndex == other.featureIndex &&
+      isLeft == other.isLeft && categories == other.categories
+    case _ => false
   }
 
   override private[tree] def toOld: OldSplit = {
@@ -181,6 +186,11 @@ final class ContinuousSplit private[ml] (override val featureIndex: Int, val thr
     }
   }
 
+  override def hashCode(): Int = {
+    val state = Seq(featureIndex, threshold)
+    state.map(Objects.hashCode).foldLeft(0)((a, b) => 31 * a + b)
+  }
+
   override private[tree] def toOld: OldSplit = {
     OldSplit(featureIndex, threshold, OldFeatureType.Continuous, List.empty[Double])
   }
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/linalg/Matrices.scala b/mllib/src/main/scala/org/apache/spark/mllib/linalg/Matrices.scala
index bb5d6d9d51..90fa4fbbc6 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/linalg/Matrices.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/linalg/Matrices.scala
@@ -606,6 +606,8 @@ class SparseMatrix @Since("1.3.0") (
     case _ => false
   }
 
+  override def hashCode(): Int = toBreeze.hashCode
+
   private[mllib] def toBreeze: BM[Double] = {
      if (!isTransposed) {
        new BSM[Double](values, numRows, numCols, colPtrs, rowIndices)
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/linalg/Vectors.scala b/mllib/src/main/scala/org/apache/spark/mllib/linalg/Vectors.scala
index 5ec83e8d5c..6e3da6b701 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/linalg/Vectors.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/linalg/Vectors.scala
@@ -628,6 +628,8 @@ class DenseVector @Since("1.0.0") (
     }
   }
 
+  override def equals(other: Any): Boolean = super.equals(other)
+
   override def hashCode(): Int = {
     var result: Int = 31 + size
     var i = 0
@@ -775,6 +777,8 @@ class SparseVector @Since("1.0.0") (
     }
   }
 
+  override def equals(other: Any): Boolean = super.equals(other)
+
   override def hashCode(): Int = {
     var result: Int = 31 + size
     val end = values.length