diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/BoundAttribute.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/BoundAttribute.scala
index 00fd7294a8966..005de3166095f 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/BoundAttribute.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/BoundAttribute.scala
@@ -46,7 +46,7 @@ case class BoundReference(ordinal: Int, dataType: DataType, nullable: Boolean)
   override def genCode(ctx: CodeGenContext, ev: GeneratedExpressionCode): Code = {
     s"""
         boolean ${ev.isNull} = i.isNullAt($ordinal);
-        ${ctx.primitiveType(dataType)} ${ev.primitive} = ${ev.isNull} ?
+        ${ctx.javaType(dataType)} ${ev.primitive} = ${ev.isNull} ?
             ${ctx.defaultValue(dataType)} : (${ctx.getColumn(dataType, ordinal)});
     """
   }
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala
index a6f805da242ab..5f76a512679a4 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala
@@ -458,7 +458,7 @@ case class Cast(child: Expression, dataType: DataType) extends UnaryExpression w
         super.genCode(ctx, ev)
 
       case (BooleanType, dt: NumericType) =>
-        defineCodeGen(ctx, ev, c => s"(${ctx.primitiveType(dt)})($c ? 1 : 0)")
+        defineCodeGen(ctx, ev, c => s"(${ctx.javaType(dt)})($c ? 1 : 0)")
       case (dt: DecimalType, BooleanType) =>
         defineCodeGen(ctx, ev, c => s"$c.isZero()")
       case (dt: NumericType, BooleanType) =>
@@ -469,7 +469,7 @@ case class Cast(child: Expression, dataType: DataType) extends UnaryExpression w
       case (_: DecimalType, dt: NumericType) =>
         defineCodeGen(ctx, ev, c => s"($c).to${ctx.boxedType(dt)}()")
       case (_: NumericType, dt: NumericType) =>
-        defineCodeGen(ctx, ev, c => s"(${ctx.primitiveType(dt)})($c)")
+        defineCodeGen(ctx, ev, c => s"(${ctx.javaType(dt)})($c)")
 
       case other =>
         super.genCode(ctx, ev)
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
index 87f864a7c0d9c..ba489f7dde59d 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
@@ -77,14 +77,13 @@ abstract class Expression extends TreeNode[Expression] {
    * @return Java source code
    */
   protected def genCode(ctx: CodeGenContext, ev: GeneratedExpressionCode): Code = {
-    val e = this.asInstanceOf[Expression]
-    ctx.references += e
+    ctx.references += this
     val objectTerm = ctx.freshName("obj")
     s"""
       /* expression: ${this} */
       Object ${objectTerm} = expressions[${ctx.references.size - 1}].eval(i);
       boolean ${ev.isNull} = ${objectTerm} == null;
-      ${ctx.primitiveType(e.dataType)} ${ev.primitive} = ${ctx.defaultValue(e.dataType)};
+      ${ctx.javaType(e.dataType)} ${ev.primitive} = ${ctx.defaultValue(e.dataType)};
       if (!${ev.isNull}) {
         ${ev.primitive} = (${ctx.boxedType(e.dataType)})${objectTerm};
       }
@@ -180,7 +179,7 @@ abstract class BinaryExpression extends Expression with trees.BinaryNode[Express
     s"""
       ${eval1.code}
       boolean ${ev.isNull} = ${eval1.isNull};
-      ${ctx.primitiveType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
+      ${ctx.javaType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
       if (!${ev.isNull}) {
         ${eval2.code}
         if(!${eval2.isNull}) {
@@ -219,7 +218,7 @@ abstract class UnaryExpression extends Expression with trees.UnaryNode[Expressio
     // reuse the previous isNull
     ev.isNull = eval.isNull
     eval.code + s"""
-      ${ctx.primitiveType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
+      ${ctx.javaType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
       if (!${ev.isNull}) {
         ${ev.primitive} = ${f(eval.primitive)};
       }
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/arithmetic.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/arithmetic.scala
index c161a514fcd4e..c983898660c0c 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/arithmetic.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/arithmetic.scala
@@ -78,7 +78,7 @@ case class Sqrt(child: Expression) extends UnaryArithmetic {
     val eval = child.gen(ctx)
     eval.code + s"""
       boolean ${ev.isNull} = ${eval.isNull};
-      ${ctx.primitiveType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
+      ${ctx.javaType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
       if (!${ev.isNull}) {
         if (${eval.primitive} < 0.0) {
           ${ev.isNull} = true;
@@ -144,7 +144,7 @@ abstract class BinaryArithmetic extends BinaryExpression {
     // byte and short are casted into int when add, minus, times or divide
     case ByteType | ShortType =>
       defineCodeGen(ctx, ev, (eval1, eval2) =>
-        s"(${ctx.primitiveType(dataType)})($eval1 $symbol $eval2)")
+        s"(${ctx.javaType(dataType)})($eval1 $symbol $eval2)")
     case _ =>
       defineCodeGen(ctx, ev, (eval1, eval2) => s"$eval1 $symbol $eval2")
   }
@@ -248,7 +248,7 @@ case class Divide(left: Expression, right: Expression) extends BinaryArithmetic
     eval1.code + eval2.code +
       s"""
       boolean ${ev.isNull} = false;
-      ${ctx.primitiveType(left.dataType)} ${ev.primitive} = ${ctx.defaultValue(left.dataType)};
+      ${ctx.javaType(left.dataType)} ${ev.primitive} = ${ctx.defaultValue(left.dataType)};
       if (${eval1.isNull} || ${eval2.isNull} || $test) {
         ${ev.isNull} = true;
       } else {
@@ -308,7 +308,7 @@ case class Remainder(left: Expression, right: Expression) extends BinaryArithmet
     eval1.code + eval2.code +
       s"""
       boolean ${ev.isNull} = false;
-      ${ctx.primitiveType(left.dataType)} ${ev.primitive} = ${ctx.defaultValue(left.dataType)};
+      ${ctx.javaType(left.dataType)} ${ev.primitive} = ${ctx.defaultValue(left.dataType)};
       if (${eval1.isNull} || ${eval2.isNull} || $test) {
         ${ev.isNull} = true;
       } else {
@@ -408,7 +408,7 @@ case class BitwiseNot(child: Expression) extends UnaryArithmetic {
   }
 
   override def genCode(ctx: CodeGenContext, ev: GeneratedExpressionCode): Code = {
-    defineCodeGen(ctx, ev, c => s"(${ctx.primitiveType(dataType)})~($c)")
+    defineCodeGen(ctx, ev, c => s"(${ctx.javaType(dataType)})~($c)")
   }
 
   protected override def evalInternal(evalE: Any) = not(evalE)
@@ -444,7 +444,7 @@ case class MaxOf(left: Expression, right: Expression) extends BinaryArithmetic {
       val eval2 = right.gen(ctx)
       eval1.code + eval2.code + s"""
         boolean ${ev.isNull} = false;
-        ${ctx.primitiveType(left.dataType)} ${ev.primitive} =
+        ${ctx.javaType(left.dataType)} ${ev.primitive} =
           ${ctx.defaultValue(left.dataType)};
 
         if (${eval1.isNull}) {
@@ -500,7 +500,7 @@ case class MinOf(left: Expression, right: Expression) extends BinaryArithmetic {
 
       eval1.code + eval2.code + s"""
         boolean ${ev.isNull} = false;
-        ${ctx.primitiveType(left.dataType)} ${ev.primitive} =
+        ${ctx.javaType(left.dataType)} ${ev.primitive} =
           ${ctx.defaultValue(left.dataType)};
 
         if (${eval1.isNull}) {
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala
index 94b1b4808d759..c8d0aaf79f5f2 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala
@@ -54,8 +54,8 @@ class CodeGenContext {
    */
   val references: mutable.ArrayBuffer[Expression] = new mutable.ArrayBuffer[Expression]()
 
-  val stringType = classOf[UTF8String].getName
-  val decimalType = classOf[Decimal].getName
+  val stringType: String = classOf[UTF8String].getName
+  val decimalType: String = classOf[Decimal].getName
 
   private val curId = new java.util.concurrent.atomic.AtomicInteger()
 
@@ -108,9 +108,9 @@ class CodeGenContext {
   }
 
   /**
-   * Return the primitive type for a DataType
+   * Return the Java type for a DataType
    */
-  def primitiveType(dt: DataType): Term = dt match {
+  def javaType(dt: DataType): Term = dt match {
     case IntegerType => "int"
     case LongType => "long"
     case ShortType => "short"
@@ -140,7 +140,7 @@ class CodeGenContext {
     case FloatType => "Float"
     case BooleanType => "Boolean"
     case DateType => "Integer"
-    case _ => primitiveType(dt)
+    case _ => javaType(dt)
   }
 
   /**
@@ -189,9 +189,9 @@ class CodeGenContext {
  */
 abstract class CodeGenerator[InType <: AnyRef, OutType <: AnyRef] extends Logging {
 
-  protected val exprType = classOf[Expression].getName
-  protected val mutableRowType = classOf[MutableRow].getName
-  protected val genericMutableRowType = classOf[GenericMutableRow].getName
+  protected val exprType: String = classOf[Expression].getName
+  protected val mutableRowType: String = classOf[MutableRow].getName
+  protected val genericMutableRowType: String = classOf[GenericMutableRow].getName
 
   /**
    * Can be flipped on manually in the console to add (expensive) expression evaluation trace code.
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GenerateProjection.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GenerateProjection.scala
index f621c894833c9..7caf4aaab88bb 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GenerateProjection.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GenerateProjection.scala
@@ -45,7 +45,7 @@ object GenerateProjection extends CodeGenerator[Seq[Expression], Projection] {
     val ctx = newCodeGenContext()
     val columns = expressions.zipWithIndex.map {
       case (e, i) =>
-        s"private ${ctx.primitiveType(e.dataType)} c$i = ${ctx.defaultValue(e.dataType)};\n"
+        s"private ${ctx.javaType(e.dataType)} c$i = ${ctx.defaultValue(e.dataType)};\n"
     }.mkString("\n      ")
 
     val initColumns = expressions.zipWithIndex.map {
@@ -80,7 +80,7 @@ object GenerateProjection extends CodeGenerator[Seq[Expression], Projection] {
       if (cases.count(_ != '\n') > 0) {
         s"""
       @Override
-      public ${ctx.primitiveType(dataType)} ${ctx.accessorForType(dataType)}(int i) {
+      public ${ctx.javaType(dataType)} ${ctx.accessorForType(dataType)}(int i) {
         if (isNullAt(i)) {
           return ${ctx.defaultValue(dataType)};
         }
@@ -103,7 +103,7 @@ object GenerateProjection extends CodeGenerator[Seq[Expression], Projection] {
       if (cases.count(_ != '\n') > 0) {
         s"""
       @Override
-      public void ${ctx.mutatorForType(dataType)}(int i, ${ctx.primitiveType(dataType)} value) {
+      public void ${ctx.mutatorForType(dataType)}(int i, ${ctx.javaType(dataType)} value) {
         nullBits[i] = false;
         switch (i) {
         $cases
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/literals.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/literals.scala
index bce96bd3c1309..3a9271678bc9c 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/literals.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/literals.scala
@@ -121,7 +121,7 @@ case class Literal protected (value: Any, dataType: DataType) extends LeafExpres
 
         case ByteType | ShortType =>  // This must go before NumericType
           ev.isNull = "false"
-          ev.primitive = s"(${ctx.primitiveType(dataType)})$value"
+          ev.primitive = s"(${ctx.javaType(dataType)})$value"
           ""
         case dt: NumericType if !dt.isInstanceOf[DecimalType] =>
           ev.isNull = "false"
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/mathfuncs/unary.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/mathfuncs/unary.scala
index ad49c376e981e..5563cd94bf86d 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/mathfuncs/unary.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/mathfuncs/unary.scala
@@ -53,7 +53,7 @@ abstract class UnaryMathExpression(f: Double => Double, name: String)
     val eval = child.gen(ctx)
     eval.code + s"""
       boolean ${ev.isNull} = ${eval.isNull};
-      ${ctx.primitiveType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
+      ${ctx.javaType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
       if (!${ev.isNull}) {
         ${ev.primitive} = java.lang.Math.${funcName}(${eval.primitive});
         if (Double.valueOf(${ev.primitive}).isNaN()) {
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/nullFunctions.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/nullFunctions.scala
index ea216b1d0d9f4..9ecfb3ccc262f 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/nullFunctions.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/nullFunctions.scala
@@ -56,7 +56,7 @@ case class Coalesce(children: Seq[Expression]) extends Expression {
   override def genCode(ctx: CodeGenContext, ev: GeneratedExpressionCode): Code = {
     s"""
       boolean ${ev.isNull} = true;
-      ${ctx.primitiveType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
+      ${ctx.javaType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
     """ +
     children.map { e =>
       val eval = e.gen(ctx)
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala
index 75af8d71dbd31..57486640c90f9 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala
@@ -397,7 +397,7 @@ case class If(predicate: Expression, trueValue: Expression, falseValue: Expressi
     s"""
       ${condEval.code}
       boolean ${ev.isNull} = false;
-      ${ctx.primitiveType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
+      ${ctx.javaType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
       if (!${condEval.isNull} && ${condEval.primitive}) {
         ${trueEval.code}
         ${ev.isNull} = ${trueEval.isNull};
@@ -530,7 +530,7 @@ case class CaseWhen(branches: Seq[Expression]) extends CaseWhenLike {
     s"""
       boolean $got = false;
       boolean ${ev.isNull} = true;
-      ${ctx.primitiveType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
+      ${ctx.javaType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
       $cases
       $other
     """
@@ -626,7 +626,7 @@ case class CaseKeyWhen(key: Expression, branches: Seq[Expression]) extends CaseW
     s"""
       boolean $got = false;
       boolean ${ev.isNull} = true;
-      ${ctx.primitiveType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
+      ${ctx.javaType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
       ${keyEval.code}
       $cases
       $other
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/sets.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/sets.scala
index 1038e7a653358..b39349b988389 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/sets.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/sets.scala
@@ -66,7 +66,7 @@ case class NewSet(elementType: DataType) extends LeafExpression {
       case IntegerType | LongType =>
         ev.isNull = "false"
         s"""
-          ${ctx.primitiveType(dataType)} ${ev.primitive} = new ${ctx.primitiveType(dataType)}();
+          ${ctx.javaType(dataType)} ${ev.primitive} = new ${ctx.javaType(dataType)}();
         """
       case _ => super.genCode(ctx, ev)
     }
@@ -109,7 +109,7 @@ case class AddItemToSet(item: Expression, set: Expression) extends Expression {
       case IntegerType | LongType =>
         val itemEval = item.gen(ctx)
         val setEval = set.gen(ctx)
-        val htype = ctx.primitiveType(dataType)
+        val htype = ctx.javaType(dataType)
 
         ev.isNull = "false"
         ev.primitive = setEval.primitive
@@ -160,7 +160,7 @@ case class CombineSets(left: Expression, right: Expression) extends BinaryExpres
       case IntegerType | LongType =>
         val leftEval = left.gen(ctx)
         val rightEval = right.gen(ctx)
-        val htype = ctx.primitiveType(dataType)
+        val htype = ctx.javaType(dataType)
 
         ev.isNull = leftEval.isNull
         ev.primitive = leftEval.primitive