ListUtil添加解构list内部的多个list为单个list的方法

hutool-core/src/main/java/org/dromara/hutool/core/collection/ListUtil.java

@@ -27,6 +27,7 @@ import org.dromara.hutool.core.util.ObjUtil;
 import java.util.*;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.function.Consumer;
+import java.util.function.Function;
 import java.util.function.Predicate;
 
 /**
@@ -748,4 +749,46 @@ public class ListUtil {
 		}
 		return resList;
 	}
+
+	/**
+	 * 解构list里面的list为单个list
+	 *
+	 * @param list 传入的list集合
+	 * @param <T>  返回的元素类型
+	 * @return 解构后的list集合
+	 */
+	public static <T> List<T> flatList(List<?> list) {
+		return flatList(list, Function.identity());
+	}
+
+	/**
+	 * 解构list里面的list，并可以对每个元素操作
+	 *
+	 * @param list      传入的list集合
+	 * @param operation 对每个元素进行操作
+	 * @param <T>       返回的元素类型
+	 * @param <O>       最内侧的元素类型
+	 * @return 解构后的list集合
+	 */
+	@SuppressWarnings("all")
+	public static <T, O> List<T> flatList(List<?> list, Function<O, T> operation) {
+		List<T> result = new ArrayList<>();
+
+		if (list == null || list.isEmpty()) {
+			return result;
+		}
+
+		if (list.get(0) instanceof List) {
+			for (List<?> subList : (List<List<?>>) list) {
+				result.addAll(flatList(subList, operation));
+			}
+		} else {
+			for (Object item : list) {
+				result.add(operation.apply((O) item));
+			}
+		}
+
+		return result;
+	}
+
 }

hutool-core/src/test/java/org/dromara/hutool/core/collection/ListUtilTest.java

@@ -2,6 +2,7 @@ package org.dromara.hutool.core.collection;
 
 import lombok.AllArgsConstructor;
 import lombok.Data;
+import org.dromara.hutool.core.convert.Convert;
 import org.dromara.hutool.core.date.StopWatch;
 import org.dromara.hutool.core.lang.Console;
 import org.dromara.hutool.core.lang.page.PageInfo;
@@ -78,7 +79,7 @@ public class ListUtilTest {
 
 	@Test
 	public void splitAvgNotZero() {
-		Assertions.assertThrows(IllegalArgumentException.class, ()->{
+		Assertions.assertThrows(IllegalArgumentException.class, () -> {
 			// limit不能小于等于0
 			ListUtil.avgPartition(Arrays.asList(1, 2, 3, 4), 0);
 		});
@@ -122,7 +123,7 @@ public class ListUtilTest {
 	public void pageTest2() {
 		final List<Integer> a = ListUtil.ofLinked(1, 2, 3, 4, 5);
 		final int[] d1 = ListUtil.page(a, PageInfo.of(a.size(), 8).setFirstPageNo(0).setPageNo(0))
-				.stream().mapToInt(Integer::valueOf).toArray();
+			.stream().mapToInt(Integer::valueOf).toArray();
 		Assertions.assertArrayEquals(new int[]{1, 2, 3, 4, 5}, d1);
 	}
 
@@ -170,11 +171,11 @@ public class ListUtilTest {
 		}
 
 		final List<TestBean> beanList = ListUtil.of(
-				new TestBean(2, "test2"),
+			new TestBean(2, "test2"),
-				new TestBean(1, "test1"),
+			new TestBean(1, "test1"),
-				new TestBean(5, "test5"),
+			new TestBean(5, "test5"),
-				new TestBean(4, "test4"),
+			new TestBean(4, "test4"),
-				new TestBean(3, "test3")
+			new TestBean(3, "test3")
 		);
 
 		final List<TestBean> order = ListUtil.sortByProperty(beanList, "order");
@@ -245,13 +246,13 @@ public class ListUtilTest {
 	}
 
 	@Test
-	public void ofCopyOnWriteTest(){
+	public void ofCopyOnWriteTest() {
 		final CopyOnWriteArrayList<String> strings = ListUtil.ofCopyOnWrite(ListUtil.of("a", "b"));
 		Assertions.assertEquals(2, strings.size());
 	}
 
 	@Test
-	public void ofCopyOnWriteTest2(){
+	public void ofCopyOnWriteTest2() {
 		final CopyOnWriteArrayList<String> strings = ListUtil.ofCopyOnWrite("a", "b");
 		Assertions.assertEquals(2, strings.size());
 	}
@@ -269,4 +270,22 @@ public class ListUtilTest {
 
 		ListUtil.reverseNew(list);
 	}
+
+	@Test
+	public void flatListTest1() {
+		List<List<List<String>>> list = Arrays.asList(Arrays.asList(Arrays.asList("1", "2", "3"), Arrays.asList("5", "6", "7")));
+
+		List<String> objects = ListUtil.flatList(list);
+
+		Assertions.assertArrayEquals(new String[]{"1", "2", "3", "5", "6", "7"}, objects.toArray());
+	}
+
+
+	@Test
+	public void flatListTest2() {
+		List<List<List<String>>> list = Arrays.asList(Arrays.asList(Arrays.asList("1", "2", "3"), Arrays.asList("5", "6", "7")));
+
+		List<Integer> objects = ListUtil.flatList(list, Convert::toInt);
+		Assertions.assertArrayEquals(new Integer[]{1, 2, 3, 5, 6, 7}, objects.toArray());
+	}
 }