From b8fbc6fc04b6f25876be0410d2662db113d49dab Mon Sep 17 00:00:00 2001
From: yulichang <570810310@qq.com>
Date: Tue, 12 Dec 2023 19:39:00 +0800
Subject: [PATCH] fix
 https://gitee.com/best_handsome/mybatis-plus-join/issues/I8NTF1

---
 .../java/com/github/yulichang/toolkit/FieldStringMap.java     | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mybatis-plus-join-core/src/main/java/com/github/yulichang/toolkit/FieldStringMap.java b/mybatis-plus-join-core/src/main/java/com/github/yulichang/toolkit/FieldStringMap.java
index 2d1196a..054ec0e 100644
--- a/mybatis-plus-join-core/src/main/java/com/github/yulichang/toolkit/FieldStringMap.java
+++ b/mybatis-plus-join-core/src/main/java/com/github/yulichang/toolkit/FieldStringMap.java
@@ -12,11 +12,11 @@ public class FieldStringMap<V> extends HashMap<String, V> {
 
     @Override
     public V get(Object key) {
-        return super.get(((String) key).toUpperCase(Locale.ENGLISH));
+        return super.get(key == null ? null : ((String) key).toUpperCase(Locale.ENGLISH));
     }
 
     @Override
     public boolean containsKey(Object key) {
-        return super.containsKey(((String) key).toUpperCase(Locale.ENGLISH));
+        return super.containsKey(key == null ? null : ((String) key).toUpperCase(Locale.ENGLISH));
     }
 }
\ No newline at end of file