From 9538041ac548f8588900ec4db819c39690dd00b7 Mon Sep 17 00:00:00 2001
From: achao <achao1441470436@gmail.com>
Date: Sun, 3 Jul 2022 17:35:54 +0800
Subject: [PATCH] =?UTF-8?q?=E5=A4=84=E7=90=86Collectors=E9=81=87=E5=88=B0n?=
 =?UTF-8?q?ull=E7=9A=84=E6=83=85=E5=86=B5?=
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---
 .../src/main/java/cn/hutool/core/stream/CollectorUtil.java | 7 ++++++-
 .../java/cn/hutool/core/collection/CollStreamUtilTest.java | 4 ++--
 2 files changed, 8 insertions(+), 3 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 1d264e744..28eb6b774 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
@@ -2,6 +2,7 @@ package cn.hutool.core.stream;
 
 import cn.hutool.core.lang.Opt;
 import cn.hutool.core.text.StrUtil;
+import cn.hutool.core.util.ArrayUtil;
 
 import java.util.Collections;
 import java.util.EnumSet;
@@ -9,6 +10,7 @@ import java.util.HashMap;
 import java.util.Map;
 import java.util.Set;
 import java.util.List;
+import java.util.Objects;
 import java.util.StringJoiner;
 import java.util.function.BiConsumer;
 import java.util.function.BinaryOperator;
@@ -104,7 +106,10 @@ public class CollectorUtil {
 		final BiConsumer<Map<K, A>, T> accumulator = (m, t) -> {
 			final K key = Opt.ofNullable(t).map(classifier).orElse(null);
 			final A container = m.computeIfAbsent(key, k -> downstreamSupplier.get());
-			downstreamAccumulator.accept(container, t);
+			if (ArrayUtil.isArray(container) || Objects.nonNull(t)) {
+				// 如果是数组类型，不需要判空，场景——分组后需要使用：java.util.stream.Collectors.counting 求null元素个数
+				downstreamAccumulator.accept(container, t);
+			}
 		};
 		final BinaryOperator<Map<K, A>> merger = mapMerger(downstream.combiner());
 		@SuppressWarnings("unchecked") final Supplier<Map<K, A>> mangledFactory = (Supplier<Map<K, A>>) mapFactory;
diff --git a/hutool-core/src/test/java/cn/hutool/core/collection/CollStreamUtilTest.java b/hutool-core/src/test/java/cn/hutool/core/collection/CollStreamUtilTest.java
index c1d5a2786..f3d1b883c 100644
--- a/hutool-core/src/test/java/cn/hutool/core/collection/CollStreamUtilTest.java
+++ b/hutool-core/src/test/java/cn/hutool/core/collection/CollStreamUtilTest.java
@@ -153,7 +153,7 @@ public class CollStreamUtilTest {
 		// 对null友好
 		final Map<Long, Map<Long, Student>> termIdClassIdStudentMap = CollStreamUtil.group2Map(Arrays.asList(null, new Student(2, 2, 1, "王五")), Student::getTermId, Student::getClassId);
 		final Map<Long, Map<Long, Student>> termIdClassIdStudentCompareMap = new HashMap<Long, Map<Long, Student>>() {{
-			put(null, MapUtil.of(null, null));
+			put(null, MapUtil.empty());
 			put(2L, MapUtil.of(2L, new Student(2, 2, 1, "王五")));
 		}};
 		Assert.assertEquals(termIdClassIdStudentCompareMap, termIdClassIdStudentMap);
@@ -215,7 +215,7 @@ public class CollStreamUtilTest {
 				new Student(1, 2, 1, "李四"));
 		final Map<Long, List<Student>> termIdStudentsMap = CollStreamUtil.groupBy(students, Student::getTermId, Collectors.toList());
 		final Map<Long, List<Student>> termIdStudentsCompareMap = new HashMap<>();
-		termIdStudentsCompareMap.put(null, Arrays.asList(null, null));
+		termIdStudentsCompareMap.put(null, Collections.emptyList());
 		termIdStudentsCompareMap.put(1L, Arrays.asList(new Student(1L, 1, 1, "张三"), new Student(1L, 2, 1, "李四")));
 		Assert.assertEquals(termIdStudentsCompareMap, termIdStudentsMap);