From 2e1c56edb010ea8c6a7eb3f6d9486ae2cf16da87 Mon Sep 17 00:00:00 2001
From: Haifeng Li <haifeng.hli@gmail.com>
Date: Fri, 22 Nov 2019 11:05:50 -0500
Subject: [PATCH] return null instead of 'null' in getString()

---
 data/src/main/java/smile/data/Tuple.java | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/data/src/main/java/smile/data/Tuple.java b/data/src/main/java/smile/data/Tuple.java
index 36b3f1ff2..aab23f35d 100644
--- a/data/src/main/java/smile/data/Tuple.java
+++ b/data/src/main/java/smile/data/Tuple.java
@@ -268,7 +268,8 @@ default double getDouble(String field) {
      * @throws ClassCastException when data type does not match.
      */
     default String getString(int i) {
-        return schema().field(i).toString(get(i));
+        Object obj = get(i);
+        return obj == null ? null : schema().field(i).toString(obj);
     }
 
     /**
@@ -277,8 +278,7 @@ default String getString(int i) {
      * @throws ClassCastException when data type does not match.
      */
     default String getString(String field) {
-        int i = fieldIndex(field);
-        return schema().field(i).toString(get(i));
+        return getString(fieldIndex(field));
     }
 
     /**