From d799e43e548da1b1affc53e879f581f5a97a087f Mon Sep 17 00:00:00 2001
From: huangchengxing <841396397@qq.com>
Date: Wed, 19 Oct 2022 11:21:31 +0800
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=E6=94=AF=E6=8C=81=E5=AF=B9?=
 =?UTF-8?q?=E5=80=BC=E9=9B=86=E5=90=88=E8=BF=9B=E8=A1=8C=E6=98=A0=E5=B0=84?=
 =?UTF-8?q?=E7=9A=84=E5=88=86=E7=BB=84=E6=96=B9=E6=B3=95?=
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---
 .../cn/hutool/core/stream/CollectorUtil.java  | 61 +++++++++++++++++++
 .../hutool/core/stream/CollectorUtilTest.java | 24 ++++++++
 2 files changed, 85 insertions(+)

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 e5374e243..71bdc4ff6 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
@@ -147,6 +147,67 @@ public class CollectorUtil {
 		return groupingBy(classifier, Collectors.toList());
 	}
 
+	/**
+	 * 提供对null值友好的groupingBy操作的{@link Collector}实现，
+	 * 对集合分组，然后对分组后的值集合进行映射
+	 *
+	 * @param classifier       分组依据
+	 * @param valueMapper      值映射方法
+	 * @param valueCollFactory 值集合的工厂方法
+	 * @param mapFactory       Map集合的工厂方法
+	 * @param <T>              元素类型
+	 * @param <K>              键类型
+	 * @param <R>              值类型
+	 * @param <C>              值集合类型
+	 * @param <M>              返回的Map集合类型
+	 * @return {@link Collector}
+	 */
+	public static <T, K, R, C extends Collection<R>, M extends Map<K, C>> Collector<T, ?, M> groupingBy(
+		final Function<? super T, ? extends K> classifier,
+		final Function<? super T, ? extends R> valueMapper,
+		final Supplier<C> valueCollFactory,
+		final Supplier<M> mapFactory) {
+		return groupingBy(classifier, mapFactory, Collectors.mapping(
+			valueMapper, Collectors.toCollection(valueCollFactory)
+		));
+	}
+
+	/**
+	 * 提供对null值友好的groupingBy操作的{@link Collector}实现，
+	 * 对集合分组，然后对分组后的值集合进行映射
+	 *
+	 * @param classifier       分组依据
+	 * @param valueMapper      值映射方法
+	 * @param valueCollFactory 值集合的工厂方法
+	 * @param <T>              元素类型
+	 * @param <K>              键类型
+	 * @param <R>              值类型
+	 * @param <C>              值集合类型
+	 * @return {@link Collector}
+	 */
+	public static <T, K, R, C extends Collection<R>> Collector<T, ?, Map<K, C>> groupingBy(
+		final Function<? super T, ? extends K> classifier,
+		final Function<? super T, ? extends R> valueMapper,
+		final Supplier<C> valueCollFactory) {
+		return groupingBy(classifier, valueMapper, valueCollFactory, HashMap::new);
+	}
+
+	/**
+	 * 提供对null值友好的groupingBy操作的{@link Collector}实现，
+	 * 对集合分组，然后对分组后的值集合进行映射
+	 *
+	 * @param classifier       分组依据
+	 * @param valueMapper      值映射方法
+	 * @param <T>              元素类型
+	 * @param <K>              键类型
+	 * @param <R>              值类型
+	 * @return {@link Collector}
+	 */
+	public static <T, K, R> Collector<T, ?, Map<K, List<R>>> groupingBy(
+		final Function<? super T, ? extends K> classifier,
+		final Function<? super T, ? extends R> valueMapper) {
+		return groupingBy(classifier, valueMapper, ArrayList::new, HashMap::new);
+	}
 
 	/**
 	 * 对null友好的 toMap 操作的 {@link Collector}实现，默认使用HashMap
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 9fb5959d9..7605a653e 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
@@ -78,4 +78,28 @@ public class CollectorUtilTest {
 				.put(3, 1L)
 				.build(), map);
 	}
+
+	@Test
+	public void testGroupingByAfterValueMapped() {
+		List<Integer> list = Arrays.asList(1, 1, 2, 2, 3, 4);
+		Map<Boolean, Set<String>> map = list.stream()
+			.collect(CollectorUtil.groupingBy(t -> (t & 1) == 0, String::valueOf, LinkedHashSet::new, LinkedHashMap::new));
+
+		Assert.assertEquals(LinkedHashMap.class, map.getClass());
+		Assert.assertEquals(new LinkedHashSet<>(Arrays.asList("2", "4")), map.get(Boolean.TRUE));
+		Assert.assertEquals(new LinkedHashSet<>(Arrays.asList("1", "3")), map.get(Boolean.FALSE));
+
+		map = list.stream()
+			.collect(CollectorUtil.groupingBy(t -> (t & 1) == 0, String::valueOf, LinkedHashSet::new));
+		Assert.assertEquals(HashMap.class, map.getClass());
+		Assert.assertEquals(new LinkedHashSet<>(Arrays.asList("2", "4")), map.get(Boolean.TRUE));
+		Assert.assertEquals(new LinkedHashSet<>(Arrays.asList("1", "3")), map.get(Boolean.FALSE));
+
+		Map<Boolean, List<String>> map2 = list.stream()
+			.collect(CollectorUtil.groupingBy(t -> (t & 1) == 0, String::valueOf));
+		Assert.assertEquals(Arrays.asList("2", "2", "4"), map2.get(Boolean.TRUE));
+		Assert.assertEquals(Arrays.asList("1", "1", "3"), map2.get(Boolean.FALSE));
+
+	}
+
 }