diff --git a/src/main/scala/ALSAlgorithm.scala b/src/main/scala/ALSAlgorithm.scala
index 3c48561..c23559f 100644
--- a/src/main/scala/ALSAlgorithm.scala
+++ b/src/main/scala/ALSAlgorithm.scala
@@ -44,6 +44,7 @@
 
   @transient lazy val logger = Logger[this.type]
 
+  override
   def train(sc: SparkContext, data: PreparedData): ALSModel = {
     require(!data.viewEvents.take(1).isEmpty,
       s"viewEvents in PreparedData cannot be empty." +
@@ -115,6 +116,7 @@
     )
   }
 
+  override
   def predict(model: ALSModel, query: Query): PredictedResult = {
 
     val productFeatures = model.productFeatures
diff --git a/src/main/scala/CooccurrenceAlgorithm.scala b/src/main/scala/CooccurrenceAlgorithm.scala
index c6e0e08..6f238ae 100644
--- a/src/main/scala/CooccurrenceAlgorithm.scala
+++ b/src/main/scala/CooccurrenceAlgorithm.scala
@@ -27,6 +27,7 @@
 class CooccurrenceAlgorithm(val ap: CooccurrenceAlgorithmParams)
   extends P2LAlgorithm[PreparedData, CooccurrenceModel, Query, PredictedResult] {
 
+  override
   def train(sc: SparkContext, data: PreparedData): CooccurrenceModel = {
 
     val itemStringIntMap = BiMap.stringInt(data.items.keys)
@@ -86,6 +87,7 @@
     topCooccurrences
   }
 
+  override
   def predict(model: CooccurrenceModel, query: Query): PredictedResult = {
 
     // convert items to Int index
diff --git a/src/main/scala/Preparator.scala b/src/main/scala/Preparator.scala
index 8c005f1..d596aa8 100644
--- a/src/main/scala/Preparator.scala
+++ b/src/main/scala/Preparator.scala
@@ -8,6 +8,7 @@
 class Preparator
   extends PPreparator[TrainingData, PreparedData] {
 
+  override
   def prepare(sc: SparkContext, trainingData: TrainingData): PreparedData = {
     new PreparedData(
       users = trainingData.users,