From 844b05cc359761c2aec31cbadc88779798936ed3 Mon Sep 17 00:00:00 2001
From: kongweiguang <kongweiguang@icourt.cc>
Date: Mon, 3 Jul 2023 09:55:23 +0800
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A0flat=E6=96=B9=E6=B3=95?=
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---
 .../dromara/hutool/core/collection/CollUtil.java  | 15 +++++++++------
 .../core/stream/TransformableWrappedStream.java   | 11 ++++++-----
 .../stream/AbstractEnhancedWrappedStreamTest.java |  2 +-
 3 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/hutool-core/src/main/java/org/dromara/hutool/core/collection/CollUtil.java b/hutool-core/src/main/java/org/dromara/hutool/core/collection/CollUtil.java
index fe8e6a768..387d6762e 100644
--- a/hutool-core/src/main/java/org/dromara/hutool/core/collection/CollUtil.java
+++ b/hutool-core/src/main/java/org/dromara/hutool/core/collection/CollUtil.java
@@ -2363,13 +2363,14 @@ public class CollUtil {
 	 * @param collection 需要解构的集合
 	 * @return 解构后的集合
 	 */
-	public static List<Object> flat(Collection<?> collection) {
+	public static <T> List<T> flat(Collection<?> collection) {
 		return flat(collection, true);
 	}
 
 	/**
 	 * 解构多层集合
-	 * 例如：List&lt;List&lt;List&lt;String&gt;&gt;&gt; 解构成 List&lt;String&gt;
+	 * 例如：例如：{@code List<List<List<String>>> 解构成 List<String>}
+	 * <p>
 	 * skipNull如果为true, 则解构后的集合里不包含null值，为false则会包含null值。
 	 *
 	 * @param collection 需要结构的集合
@@ -2377,7 +2378,7 @@ public class CollUtil {
 	 * @return 解构后的集合
 	 */
 	@SuppressWarnings({"unchecked"})
-	public static List<Object> flat(Collection<?> collection, boolean skipNull) {
+	public static <T> List<T> flat(Collection<?> collection, boolean skipNull) {
 		LinkedList<Object> queue = new LinkedList<>(collection);
 
 		List<Object> result = new ArrayList<>();
@@ -2385,14 +2386,16 @@ public class CollUtil {
 		while (!queue.isEmpty()) {
 			Object t = queue.removeFirst();
 
+			if (skipNull && t == null) {
+				continue;
+			}
+
 			if (t instanceof Collection) {
 				queue.addAll((Collection<?>) t);
-			} else if (skipNull && t == null) {
-				continue;
 			} else {
 				result.add(t);
 			}
 		}
-		return result;
+		return (List<T>) result;
 	}
 }
diff --git a/hutool-core/src/main/java/org/dromara/hutool/core/stream/TransformableWrappedStream.java b/hutool-core/src/main/java/org/dromara/hutool/core/stream/TransformableWrappedStream.java
index 2843f7303..718472d1c 100644
--- a/hutool-core/src/main/java/org/dromara/hutool/core/stream/TransformableWrappedStream.java
+++ b/hutool-core/src/main/java/org/dromara/hutool/core/stream/TransformableWrappedStream.java
@@ -489,14 +489,15 @@ public interface TransformableWrappedStream<T, S extends TransformableWrappedStr
 
 	/**
 	 * 如果当前元素是集合，则会将集合中的元素解构出来
-	 * 例如：List&lt;List&lt;List&lt;String&gt;&gt;&gt; 解构成 List&lt;String&gt;
-	 * @param clazz 解构后元素的类型
-	 * @param <R>   函数执行后返回的类型
+	 * 例如：{@code List<List<List<String>>> 解构成 List<String>}
+	 *
+	 * @param <R> 函数执行后返回的List里面的类型
 	 * @return EasyStream 一个流
 	 */
-	default <R> EasyStream<R> flatObj(Class<R> clazz) {
-		return EasyStream.of(CollUtil.flat(nonNull().collect(Collectors.toList()))).map(clazz::cast);
+	default <R> EasyStream<R> flat() {
+		return EasyStream.of(CollUtil.flat(nonNull().collect(Collectors.toList())));
 	}
+
 	// endregion
 
 	// region ============ map ============
diff --git a/hutool-core/src/test/java/org/dromara/hutool/core/stream/AbstractEnhancedWrappedStreamTest.java b/hutool-core/src/test/java/org/dromara/hutool/core/stream/AbstractEnhancedWrappedStreamTest.java
index 261b00dca..1c64f3299 100644
--- a/hutool-core/src/test/java/org/dromara/hutool/core/stream/AbstractEnhancedWrappedStreamTest.java
+++ b/hutool-core/src/test/java/org/dromara/hutool/core/stream/AbstractEnhancedWrappedStreamTest.java
@@ -723,7 +723,7 @@ public class AbstractEnhancedWrappedStreamTest {
 				Arrays.asList("j", "k", "l")
 			)
 		);
-		List<String> r = EasyStream.of(list).flatObj(String.class).toList();
+		List<String> r = EasyStream.of(list).<String>flat().toList();
 		Assertions.assertArrayEquals(new String[]{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l"}, r.toArray());
 	}