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 978c94132ac17..a8681d57f208e 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
@@ -437,17 +437,17 @@ case class Cast(child: Expression, dataType: DataType) extends UnaryExpression w
 
       case (BinaryType, StringType) =>
         defineCodeGen (ctx, ev, c =>
-          s"${ctx.stringType}().fromBytes($c)")
+          s"${ctx.stringType}.fromBytes($c)")
       case (DateType, StringType) =>
         defineCodeGen(ctx, ev, c =>
-          s"""${ctx.stringType}().fromString(
+          s"""${ctx.stringType}.fromString(
                 org.apache.spark.sql.catalyst.util.DateUtils.toString($c))""")
       // Special handling required for timestamps in hive test cases since the toString function
       // does not match the expected output.
       case (TimestampType, StringType) =>
         super.genCode(ctx, ev)
       case (_, StringType) =>
-        defineCodeGen(ctx, ev, c => s"${ctx.stringType}().fromString(String.valueOf($c))")
+        defineCodeGen(ctx, ev, c => s"${ctx.stringType}.fromString(String.valueOf($c))")
 
       // fallback for DecimalType, this must be before other numeric types
       case (_, dt: DecimalType) =>
diff --git a/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java b/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
index f9a378c50130b..9871a70a40e69 100644
--- a/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
+++ b/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
@@ -20,7 +20,7 @@
 import java.io.Serializable;
 import java.io.UnsupportedEncodingException;
 import java.util.Arrays;
-import javax.annotation.Nullable;
+import javax.annotation.Nonnull;
 
 import org.apache.spark.unsafe.PlatformDependent;
 
@@ -34,7 +34,7 @@
  */
 public final class UTF8String implements Comparable<UTF8String>, Serializable {
 
-  @Nullable
+  @Nonnull
   private byte[] bytes;
 
   private static int[] bytesOfCodePointInUTF8 = {2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,