Apply suggestions from code review

Author: balamurugana

api/src/main/java/io/minio/messages/Item.java

@@ -21,7 +21,6 @@
 import java.nio.charset.StandardCharsets;
 import java.time.ZonedDateTime;
 import java.util.Map;
-import java.util.Optional;
 import org.simpleframework.xml.Element;
 
 /**
@@ -87,9 +86,7 @@ public String objectName() {
 
   /** Returns last modified time of the object. */
   public ZonedDateTime lastModified() {
-    return Optional.ofNullable(lastModified)
-      .map(ResponseDate::zonedDateTime)
-      .orElse(null);
+    return (lastModified == null) ? null : lastModified.zonedDateTime();
   }
 
   /** Returns ETag of the object. */
@@ -114,9 +111,7 @@ public Owner owner() {
 
   /** Returns user metadata. This is MinIO specific extension to ListObjectsV2. */
   public Map<String, String> userMetadata() {
-    return Optional.ofNullable(userMetadata)
-      .map(Metadata::get)
-      .orElse(null);
+    return (userMetadata == null) ? null : userMetadata.get();
   }
 
   public String userTags() {