Use pattern match in createNullValue

Author: zsxwing

core/src/main/scala/org/apache/spark/util/ClosureCleaner.scala

@@ -109,15 +109,13 @@ private[spark] object ClosureCleaner extends Logging {
 
   private def createNullValue(cls: Class[_]): AnyRef = {
     if (cls.isPrimitive) {
-      if (cls == java.lang.Boolean.TYPE) {
-        new java.lang.Boolean(false)
-      } else if (cls == java.lang.Character.TYPE) {
-        new java.lang.Character('\0')
-      } else if (cls == java.lang.Void.TYPE) {
-        // It should not happen because `Foo(void x) {}` won't be compiled.
-        throw new IllegalStateException("This should not happen")
-      } else {
-        new java.lang.Byte(0: Byte)
+      cls match {
+        case java.lang.Boolean.TYPE => new java.lang.Boolean(false)
+        case java.lang.Character.TYPE => new java.lang.Character('\0')
+        case java.lang.Void.TYPE =>
+          // This should not happen because `Foo(void x) {}` cannot be compiled.
+          throw new IllegalStateException("This should not happen")
+        case _ => new java.lang.Byte(0: Byte)
       }
     } else {
       null