diff --git a/scala-package/core/src/test/scala/org/apache/mxnet/ImageSuite.scala b/scala-package/core/src/test/scala/org/apache/mxnet/ImageSuite.scala
index d4cf35af186f..dca4ce02ef89 100644
--- a/scala-package/core/src/test/scala/org/apache/mxnet/ImageSuite.scala
+++ b/scala-package/core/src/test/scala/org/apache/mxnet/ImageSuite.scala
@@ -57,7 +57,7 @@ class ImageSuite extends FunSuite with BeforeAndAfterAll {
 
   test("Test load image") {
     val nd = Image.imRead(imLocation)
-    logger.info(s"OpenCV load image with shape: ${nd.shape}")
+    logger.debug(s"OpenCV load image with shape: ${nd.shape}")
     require(nd.shape == Shape(576, 1024, 3), "image shape not Match!")
   }
 
@@ -65,14 +65,14 @@ class ImageSuite extends FunSuite with BeforeAndAfterAll {
     val url = new URL("https://s3.amazonaws.com/model-server/inputs/Pug-Cookie.jpg")
     val inputStream = url.openStream
     val nd = Image.imDecode(inputStream)
-    logger.info(s"OpenCV load image with shape: ${nd.shape}")
+    logger.debug(s"OpenCV load image with shape: ${nd.shape}")
     require(nd.shape == Shape(576, 1024, 3), "image shape not Match!")
   }
 
   test("Test resize image") {
     val nd = Image.imRead(imLocation)
     val resizeIm = Image.imResize(nd, 224, 224)
-    logger.info(s"OpenCV resize image with shape: ${resizeIm.shape}")
+    logger.debug(s"OpenCV resize image with shape: ${resizeIm.shape}")
     require(resizeIm.shape == Shape(224, 224, 3), "image shape not Match!")
   }
 
@@ -94,7 +94,7 @@ class ImageSuite extends FunSuite with BeforeAndAfterAll {
     val tempDirPath = System.getProperty("java.io.tmpdir")
     val img = Image.toImage(resizeIm)
     ImageIO.write(img, "png", new File(tempDirPath + "/inputImages/out.png"))
-    logger.info(s"converted image stored in ${tempDirPath + "/inputImages/out.png"}")
+    logger.debug(s"converted image stored in ${tempDirPath + "/inputImages/out.png"}")
   }
 
   test("Test draw Bounding box") {
@@ -107,7 +107,7 @@ class ImageSuite extends FunSuite with BeforeAndAfterAll {
     Image.drawBoundingBox(buf, box, Some(names), fontSizeMult = Some(1.4f))
     val tempDirPath = System.getProperty("java.io.tmpdir")
     ImageIO.write(buf, "png", new File(tempDirPath + "/inputImages/out2.png"))
-    logger.info(s"converted image stored in ${tempDirPath + "/inputImages/out2.png"}")
+    logger.debug(s"converted image stored in ${tempDirPath + "/inputImages/out2.png"}")
     for (coord <- box) {
       val topLeft = buf.getRGB(coord("xmin"), coord("ymin"))
       val downLeft = buf.getRGB(coord("xmin"), coord("ymax"))
diff --git a/scala-package/core/src/test/scala/org/apache/mxnet/KVStoreSuite.scala b/scala-package/core/src/test/scala/org/apache/mxnet/KVStoreSuite.scala
index 2e1b36c5b162..3eb61414bac1 100644
--- a/scala-package/core/src/test/scala/org/apache/mxnet/KVStoreSuite.scala
+++ b/scala-package/core/src/test/scala/org/apache/mxnet/KVStoreSuite.scala
@@ -67,9 +67,6 @@ class KVStoreSuite extends FunSuite with BeforeAndAfterAll {
     val kv = KVStore.create()
     val updater = new MXKVStoreUpdater {
       override def update(key: Int, input: NDArray, stored: NDArray): Unit = {
-        // scalastyle:off println
-        println(s"update on key $key")
-        // scalastyle:on println
         stored += input * 2
       }
       override def dispose(): Unit = {}
diff --git a/scala-package/core/src/test/scala/org/apache/mxnet/ModelParallelSuite.scala b/scala-package/core/src/test/scala/org/apache/mxnet/ModelParallelSuite.scala
index 8ed1dc4c2332..2962e3b4781c 100644
--- a/scala-package/core/src/test/scala/org/apache/mxnet/ModelParallelSuite.scala
+++ b/scala-package/core/src/test/scala/org/apache/mxnet/ModelParallelSuite.scala
@@ -58,11 +58,6 @@ class ModelParallelSuite extends FunSuite with BeforeAndAfterAll {
     val arrGrad2 = arrGrad.map(_.copyTo(ctx1))
     val exec2 = net.bind(ctx1, args = arr2, argsGrad = arrGrad2)
 
-    // Show the execution plan that involves copynode
-    // scalastyle:off println
-    print(exec1.debugStr)
-    // scalastyle:on println
-
     exec1.forward()
     exec2.forward()
     assert(reldiff(exec1.outputs(0).copyTo(ctx1),
diff --git a/scala-package/core/src/test/scala/org/apache/mxnet/OperatorSuite.scala b/scala-package/core/src/test/scala/org/apache/mxnet/OperatorSuite.scala
index dd5f96f980a6..deb149985ce8 100644
--- a/scala-package/core/src/test/scala/org/apache/mxnet/OperatorSuite.scala
+++ b/scala-package/core/src/test/scala/org/apache/mxnet/OperatorSuite.scala
@@ -614,9 +614,6 @@ class OperatorSuite extends FunSuite with BeforeAndAfterAll
     val embed = Symbol.Embedding(name = "embed")()(
       Map("data" -> data, "input_dim" -> inDim, "output_dim" -> outDim))
     // TODO
-    // scalastyle:off println
-    println(s"Embeded symbol: ${embed.toJson}")
-    // scalastyle:on println
   }
 
   // check ops handle duplicate input correctly.
@@ -983,9 +980,6 @@ class OperatorSuite extends FunSuite with BeforeAndAfterAll
   test("batch norm") {
     val data = Symbol.Variable("data")
     val test = Symbol.BatchNorm(name = "bn")()(Map("data" -> data, "fix_gamma" -> "False"))
-    // scalastyle:off println
-    println(s"BatchNorm: ${test.toJson}")
-    // scalastyle:on println
     // TODO: check numeric gradient
   }
 
diff --git a/scala-package/core/src/test/scala/org/apache/mxnet/SymbolSuite.scala b/scala-package/core/src/test/scala/org/apache/mxnet/SymbolSuite.scala
index d134c83ff7e7..415be5122c95 100644
--- a/scala-package/core/src/test/scala/org/apache/mxnet/SymbolSuite.scala
+++ b/scala-package/core/src/test/scala/org/apache/mxnet/SymbolSuite.scala
@@ -32,14 +32,8 @@ class SymbolSuite extends FunSuite with BeforeAndAfterAll {
     var net2 = Symbol.FullyConnected(name = "fc3")()(Map("num_hidden" -> 10))
     net2 = Symbol.Activation()()(Map("data" -> net2, "act_type" -> "relu"))
     net2 = Symbol.FullyConnected(name = "fc4")()(Map("data" -> net2, "num_hidden" -> 20))
-    // scalastyle:off println
-    println(s"net2 debug info:\n${net2.debugStr}")
-    // scalastyle:on println
 
     val composed = net2(name = "composed", Map("fc3_data" -> net1))
-    // scalastyle:off println
-    println(s"composed debug info:\n${composed.debugStr}")
-    // scalastyle:on println
     val multiOut = Symbol.Group(composed, net1)
     assert(multiOut.listOutputs().length === 2)
   }
@@ -77,10 +71,6 @@ class SymbolSuite extends FunSuite with BeforeAndAfterAll {
     val lam = Symbol.Variable("lam")
     val rnd = Symbol.random.poisson(lam = Some(lam), shape = Some(Shape(2, 2)))
     val rnd2 = Symbol.random.poisson(lam = Some(1f), shape = Some(Shape(2, 2)))
-    // scalastyle:off println
-    println(s"Symbol.random.poisson debug info: ${rnd.debugStr}")
-    println(s"Symbol.random.poisson debug info: ${rnd2.debugStr}")
-    // scalastyle:on println
   }
 
   test("Symbol random module is generated properly - special case of 'normal'") {
@@ -88,9 +78,5 @@ class SymbolSuite extends FunSuite with BeforeAndAfterAll {
     val scale = Symbol.Variable("scale")
     val rnd = Symbol.random.normal(mu = Some(loc), sigma = Some(scale), shape = Some(Shape(2, 2)))
     val rnd2 = Symbol.random.normal(mu = Some(1f), sigma = Some(2f), shape = Some(Shape(2, 2)))
-    // scalastyle:off println
-    println(s"Symbol.random.sample_normal debug info: ${rnd.debugStr}")
-    println(s"Symbol.random.random_normal debug info: ${rnd2.debugStr}")
-    // scalastyle:on println
   }
 }
diff --git a/scala-package/macros/src/main/scala/org/apache/mxnet/GeneratorBase.scala b/scala-package/macros/src/main/scala/org/apache/mxnet/GeneratorBase.scala
index 498c4e943669..b2033f529c65 100644
--- a/scala-package/macros/src/main/scala/org/apache/mxnet/GeneratorBase.scala
+++ b/scala-package/macros/src/main/scala/org/apache/mxnet/GeneratorBase.scala
@@ -116,7 +116,7 @@ private[mxnet] abstract class GeneratorBase {
     */
   protected def structGeneration(c: blackbox.Context)
                                 (funcDef: List[c.universe.DefDef], annottees: c.Expr[Any]*)
-  : c.Expr[Any] = {
+  : c.Expr[Nothing] = {
     import c.universe._
     val inputs = annottees.map(_.tree).toList
     // pattern match on the inputs
diff --git a/scala-package/macros/src/main/scala/org/apache/mxnet/NDArrayMacro.scala b/scala-package/macros/src/main/scala/org/apache/mxnet/NDArrayMacro.scala
index c18694b59bf6..f5b8bce11cf5 100644
--- a/scala-package/macros/src/main/scala/org/apache/mxnet/NDArrayMacro.scala
+++ b/scala-package/macros/src/main/scala/org/apache/mxnet/NDArrayMacro.scala
@@ -22,15 +22,16 @@ import scala.language.experimental.macros
 import scala.reflect.macros.blackbox
 
 private[mxnet] class AddNDArrayFunctions(isContrib: Boolean) extends StaticAnnotation {
-  private[mxnet] def macroTransform(annottees: Any*) = macro NDArrayMacro.addDefs
+  private[mxnet] def macroTransform(annottees: Any*): Any = macro NDArrayMacro.addDefs
 }
 
 private[mxnet] class AddNDArrayAPIs(isContrib: Boolean) extends StaticAnnotation {
-  private[mxnet] def macroTransform(annottees: Any*) = macro TypedNDArrayAPIMacro.typeSafeAPIDefs
+  private[mxnet] def macroTransform(annottees: Any*): Any =
+  macro TypedNDArrayAPIMacro.typeSafeAPIDefs
 }
 
 private[mxnet] class AddNDArrayRandomAPIs(isContrib: Boolean) extends StaticAnnotation {
-  private[mxnet] def macroTransform(annottees: Any*) =
+  private[mxnet] def macroTransform(annottees: Any*): Any =
   macro TypedNDArrayRandomAPIMacro.typeSafeAPIDefs
 }
 
@@ -39,7 +40,7 @@ private[mxnet] class AddNDArrayRandomAPIs(isContrib: Boolean) extends StaticAnno
   */
 private[mxnet] object NDArrayMacro extends GeneratorBase {
 
-  def addDefs(c: blackbox.Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
+  def addDefs(c: blackbox.Context)(annottees: c.Expr[Any]*): c.Expr[Nothing] = {
     import c.universe._
     val isContrib: Boolean = c.prefix.tree match {
       case q"new AddNDArrayFunctions($b)" => c.eval[Boolean](c.Expr(b))
@@ -49,7 +50,7 @@ private[mxnet] object NDArrayMacro extends GeneratorBase {
   }
 
   private def impl(c: blackbox.Context)
-                  (isContrib: Boolean, annottees: c.Expr[Any]*): c.Expr[Any] = {
+                  (isContrib: Boolean, annottees: c.Expr[Any]*): c.Expr[Nothing] = {
     import c.universe._
 
     val functions = functionsToGenerate(isSymbol = false, isContrib)
@@ -82,7 +83,7 @@ private[mxnet] object NDArrayMacro extends GeneratorBase {
   */
 private[mxnet] object TypedNDArrayAPIMacro extends GeneratorBase {
 
-  def typeSafeAPIDefs(c: blackbox.Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
+  def typeSafeAPIDefs(c: blackbox.Context)(annottees: c.Expr[Any]*): c.Expr[Nothing] = {
     import c.universe._
     val isContrib: Boolean = c.prefix.tree match {
       case q"new AddNDArrayAPIs($b)" => c.eval[Boolean](c.Expr(b))
@@ -148,7 +149,7 @@ private[mxnet] object TypedNDArrayAPIMacro extends GeneratorBase {
 private[mxnet] object TypedNDArrayRandomAPIMacro extends GeneratorBase
   with RandomHelpers {
 
-  def typeSafeAPIDefs(c: blackbox.Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
+  def typeSafeAPIDefs(c: blackbox.Context)(annottees: c.Expr[Any]*): c.Expr[Nothing] = {
     // Note: no contrib managed in this module
 
     val functionDefs = typeSafeRandomFunctionsToGenerate(isSymbol = false)
diff --git a/scala-package/macros/src/main/scala/org/apache/mxnet/SymbolMacro.scala b/scala-package/macros/src/main/scala/org/apache/mxnet/SymbolMacro.scala
index 7ec80b9c066c..06b567c3d2d4 100644
--- a/scala-package/macros/src/main/scala/org/apache/mxnet/SymbolMacro.scala
+++ b/scala-package/macros/src/main/scala/org/apache/mxnet/SymbolMacro.scala
@@ -23,15 +23,16 @@ import scala.language.experimental.macros
 import scala.reflect.macros.blackbox
 
 private[mxnet] class AddSymbolFunctions(isContrib: Boolean) extends StaticAnnotation {
-  private[mxnet] def macroTransform(annottees: Any*) = macro SymbolMacro.addDefs
+  private[mxnet] def macroTransform(annottees: Any*): Any = macro SymbolMacro.addDefs
 }
 
 private[mxnet] class AddSymbolAPIs(isContrib: Boolean) extends StaticAnnotation {
-  private[mxnet] def macroTransform(annottees: Any*) = macro TypedSymbolAPIMacro.typeSafeAPIDefs
+  private[mxnet] def macroTransform(annottees: Any*): Any =
+  macro TypedSymbolAPIMacro.typeSafeAPIDefs
 }
 
 private[mxnet] class AddSymbolRandomAPIs(isContrib: Boolean) extends StaticAnnotation {
-  private[mxnet] def macroTransform(annottees: Any*) =
+  private[mxnet] def macroTransform(annottees: Any*): Any =
   macro TypedSymbolRandomAPIMacro.typeSafeAPIDefs
 }
 
@@ -40,7 +41,7 @@ private[mxnet] class AddSymbolRandomAPIs(isContrib: Boolean) extends StaticAnnot
   */
 private[mxnet] object SymbolMacro extends GeneratorBase {
 
-  def addDefs(c: blackbox.Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
+  def addDefs(c: blackbox.Context)(annottees: c.Expr[Any]*): c.Expr[Nothing] = {
     import c.universe._
     val isContrib: Boolean = c.prefix.tree match {
       case q"new AddSymbolFunctions($b)" => c.eval[Boolean](c.Expr(b))
@@ -50,7 +51,7 @@ private[mxnet] object SymbolMacro extends GeneratorBase {
   }
 
   private def impl(c: blackbox.Context)
-                  (isContrib: Boolean, annottees: c.Expr[Any]*): c.Expr[Any] = {
+                  (isContrib: Boolean, annottees: c.Expr[Any]*): c.Expr[Nothing] = {
     import c.universe._
 
     val functions = functionsToGenerate(isSymbol = false, isContrib)
@@ -76,7 +77,7 @@ private[mxnet] object SymbolMacro extends GeneratorBase {
   */
 private[mxnet] object TypedSymbolAPIMacro extends GeneratorBase {
 
-  def typeSafeAPIDefs(c: blackbox.Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
+  def typeSafeAPIDefs(c: blackbox.Context)(annottees: c.Expr[Any]*): c.Expr[Nothing] = {
     import c.universe._
     val isContrib: Boolean = c.prefix.tree match {
       case q"new AddSymbolAPIs($b)" => c.eval[Boolean](c.Expr(b))
@@ -140,7 +141,7 @@ private[mxnet] object TypedSymbolAPIMacro extends GeneratorBase {
 private[mxnet] object TypedSymbolRandomAPIMacro extends GeneratorBase
   with RandomHelpers {
 
-  def typeSafeAPIDefs(c: blackbox.Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
+  def typeSafeAPIDefs(c: blackbox.Context)(annottees: c.Expr[Any]*): c.Expr[Nothing] = {
     val functionDefs = typeSafeRandomFunctionsToGenerate(isSymbol = true)
       .map(f => buildTypedFunction(c)(f))
 
diff --git a/scala-package/macros/src/main/scala/org/apache/mxnet/javaapi/JavaNDArrayMacro.scala b/scala-package/macros/src/main/scala/org/apache/mxnet/javaapi/JavaNDArrayMacro.scala
index fa3565b4fb8e..9bf0818c14a4 100644
--- a/scala-package/macros/src/main/scala/org/apache/mxnet/javaapi/JavaNDArrayMacro.scala
+++ b/scala-package/macros/src/main/scala/org/apache/mxnet/javaapi/JavaNDArrayMacro.scala
@@ -25,18 +25,16 @@ import scala.language.experimental.macros
 import scala.reflect.macros.blackbox
 
 private[mxnet] class AddJNDArrayAPIs(isContrib: Boolean) extends StaticAnnotation {
-  private[mxnet] def macroTransform(annottees: Any*) = macro JavaNDArrayMacro.typeSafeAPIDefs
+  private[mxnet] def macroTransform(annottees: Any*): Any = macro JavaNDArrayMacro.typeSafeAPIDefs
 }
 
 private[mxnet] object JavaNDArrayMacro extends GeneratorBase {
 
-  // scalastyle:off havetype
-  def typeSafeAPIDefs(c: blackbox.Context)(annottees: c.Expr[Any]*) = {
+  def typeSafeAPIDefs(c: blackbox.Context)(annottees: c.Expr[Any]*): c.Expr[Nothing] = {
     typeSafeAPIImpl(c)(annottees: _*)
   }
-  // scalastyle:off havetype
 
-  private def typeSafeAPIImpl(c: blackbox.Context)(annottees: c.Expr[Any]*) : c.Expr[Any] = {
+  private def typeSafeAPIImpl(c: blackbox.Context)(annottees: c.Expr[Any]*) : c.Expr[Nothing] = {
     import c.universe._
 
     val isContrib: Boolean = c.prefix.tree match {
diff --git a/scala-package/spark/src/main/scala/org/apache/mxnet/spark/MXNDArray.scala b/scala-package/spark/src/main/scala/org/apache/mxnet/spark/MXNDArray.scala
index a18c47d78741..0d4c18c2b8e9 100644
--- a/scala-package/spark/src/main/scala/org/apache/mxnet/spark/MXNDArray.scala
+++ b/scala-package/spark/src/main/scala/org/apache/mxnet/spark/MXNDArray.scala
@@ -20,7 +20,7 @@ package org.apache.mxnet.spark
 import org.apache.mxnet.NDArray
 
 /**
- * A wrapper for serialize & deserialize <pre>[[org.apache.mxnet.NDArray]]</pre> in spark job
+ * A wrapper for serialize & deserialize ``org.apache.mxnet.NDArray`` in spark job
  * @author Yizhi Liu
  */
 class MXNDArray(@transient private var ndArray: NDArray) extends Serializable {
diff --git a/scala-package/spark/src/main/scala/org/apache/mxnet/spark/MXNetModel.scala b/scala-package/spark/src/main/scala/org/apache/mxnet/spark/MXNetModel.scala
index 2c4c8fe42780..234e9a597cf5 100644
--- a/scala-package/spark/src/main/scala/org/apache/mxnet/spark/MXNetModel.scala
+++ b/scala-package/spark/src/main/scala/org/apache/mxnet/spark/MXNetModel.scala
@@ -23,7 +23,7 @@ import org.apache.spark.SparkContext
 import org.apache.spark.mllib.linalg.Vector
 
 /**
- * Wrapper for <pre>[[org.apache.mxnet.Model]]</pre> which used in Spark application
+ * Wrapper for ``org.apache.mxnet.Model`` which used in Spark application
  * @author Yizhi Liu
  */
 class MXNetModel private[mxnet](