From 6a97f12eb07fdebf429ad7836947ce23dc9e8442 Mon Sep 17 00:00:00 2001
From: VampireAchao <achao@hutool.cn>
Date: Sun, 12 Nov 2023 16:33:31 +0800
Subject: [PATCH] =?UTF-8?q?[Fix]=20=E4=BF=AE=E5=A4=8D=20github=20issue=203?=
 =?UTF-8?q?380=20CollectorUtil.reduceListMap=E4=B8=8Ecollectors.groupby?=
 =?UTF-8?q?=E4=B8=80=E8=B5=B7=E4=BD=BF=E7=94=A8=E6=97=B6=E5=87=BA=E7=8E=B0?=
 =?UTF-8?q?=E4=B8=8E=E9=A2=84=E6=9C=9F=E4=B8=8D=E7=AC=A6=E7=9A=84=E7=BB=93?=
 =?UTF-8?q?=E6=9E=9C?=
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---
 .../cn/hutool/core/stream/CollectorUtil.java    |  9 +++++++--
 .../hutool/core/stream/CollectorUtilTest.java   | 17 +++++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/hutool-core/src/main/java/cn/hutool/core/stream/CollectorUtil.java b/hutool-core/src/main/java/cn/hutool/core/stream/CollectorUtil.java
index f474c53ea..a1bf57f09 100644
--- a/hutool-core/src/main/java/cn/hutool/core/stream/CollectorUtil.java
+++ b/hutool-core/src/main/java/cn/hutool/core/stream/CollectorUtil.java
@@ -243,8 +243,13 @@ public class CollectorUtil {
 					value.forEach((k, v) -> result.computeIfAbsent(k, i -> new ArrayList<>()).add(v));
 					return result;
 				}, (l, r) -> {
-					r.forEach((k, v) -> l.computeIfAbsent(k, i -> new ArrayList<>()).addAll(v));
-					return l;
+					R resultMap = mapSupplier.get();
+					resultMap.putAll(l);
+					r.forEach((k, v) -> {
+						List<V> list = resultMap.computeIfAbsent(k, i -> new ArrayList<>());
+						list.addAll(v);
+					});
+					return resultMap;
 				}
 		);
 	}
diff --git a/hutool-core/src/test/java/cn/hutool/core/stream/CollectorUtilTest.java b/hutool-core/src/test/java/cn/hutool/core/stream/CollectorUtilTest.java
index bd8a415ba..c79d7f494 100644
--- a/hutool-core/src/test/java/cn/hutool/core/stream/CollectorUtilTest.java
+++ b/hutool-core/src/test/java/cn/hutool/core/stream/CollectorUtilTest.java
@@ -1,5 +1,6 @@
 package cn.hutool.core.stream;
 
+import cn.hutool.core.collection.ListUtil;
 import cn.hutool.core.map.MapUtil;
 import org.junit.Assert;
 import org.junit.Test;
@@ -29,6 +30,22 @@ public class CollectorUtilTest {
 		Assert.assertEquals(MapUtil.builder("苏格拉底", Arrays.asList(1, 2))
 						.put("特拉叙马霍斯", Arrays.asList(3, 1, 2)).build(),
 				nameScoresMap);
+
+		List<Map<String, String>> data = ListUtil.toList(
+			MapUtil.builder("name", "sam").put("count", "80").map(),
+			MapUtil.builder("name", "sam").put("count", "81").map(),
+			MapUtil.builder("name", "sam").put("count", "82").map(),
+			MapUtil.builder("name", "jack").put("count", "80").map(),
+			MapUtil.builder("name", "jack").put("count", "90").map()
+		);
+
+		Map<String, Map<String, List<String>>> nameMap = data.stream()
+			.collect(Collectors.groupingBy(e -> e.get("name"), CollectorUtil.reduceListMap()));
+		Assert.assertEquals(MapUtil.builder("jack", MapUtil.builder("name", Arrays.asList("jack", "jack"))
+				.put("count", Arrays.asList("80", "90")).build())
+			.put("sam", MapUtil.builder("name", Arrays.asList("sam", "sam", "sam"))
+				.put("count", Arrays.asList("80", "81", "82")).build())
+			.build(), nameMap);
 	}
 
 	@Test