From 59f33fd12d6879ca87568517eb878466b3a0e92b Mon Sep 17 00:00:00 2001
From: Looly <loolly@aliyun.com>
Date: Wed, 30 Jul 2025 19:14:23 +0800
Subject: [PATCH] =?UTF-8?q?`MapUtil`=E5=A2=9E=E5=8A=A0flatten=E6=96=B9?=
 =?UTF-8?q?=E6=B3=95=EF=BC=88pr#1368@Gitee=EF=BC=89?=
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---
 .../src/main/java/cn/hutool/core/map/MapUtil.java     | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/hutool-core/src/main/java/cn/hutool/core/map/MapUtil.java b/hutool-core/src/main/java/cn/hutool/core/map/MapUtil.java
index 985c307f1..1128b510d 100755
--- a/hutool-core/src/main/java/cn/hutool/core/map/MapUtil.java
+++ b/hutool-core/src/main/java/cn/hutool/core/map/MapUtil.java
@@ -1549,9 +1549,10 @@ public class MapUtil {
 	 * 将多层级Map处理为一个层级Map类型
 	 *
 	 * @param map 入参Map
+	 * @param <K> 键类型
+	 * @param <V> 值类型
 	 * @return 单层级Map返回值
-	 * @param <K>  键类型
-	 * @param <V>  值类型
+	 * @since 5.8.40
 	 */
 	public static <K, V> Map<K, V> flatten(final Map<K, V> map) {
 		return flatten(map, new HashMap<>());
@@ -1565,17 +1566,19 @@ public class MapUtil {
 	 * @param <K>     键类型
 	 * @param <V>     值类型
 	 * @return 单层级Map返回值
+	 * @since 5.8.40
 	 */
 	@SuppressWarnings("unchecked")
 	public static <K, V> Map<K, V> flatten(final Map<K, V> map, Map<K, V> flatMap) {
 		Assert.notNull(map);
-		if(null == flatMap){
+		if (null == flatMap) {
 			flatMap = new HashMap<>();
 		}
 
 		Map<K, V> finalFlatMap = flatMap;
 		map.forEach((k, v) -> {
-			if (v instanceof Map) {
+			// 避免嵌套循环
+			if (v instanceof Map && v != map) {
 				flatten((Map<K, V>) v, finalFlatMap);
 			} else {
 				finalFlatMap.put(k, v);