TreeUtil.buildSingle指定rootId节点存在时，作为根节点

hutool-core/src/main/java/org/dromara/hutool/core/tree/TreeBuilder.java

@@ -23,6 +23,7 @@ import org.dromara.hutool.core.map.MapUtil;
 import org.dromara.hutool.core.tree.parser.NodeParser;
 import org.dromara.hutool.core.util.ObjUtil;
 
+import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -35,7 +36,7 @@ import java.util.Map;
 public class TreeBuilder<E> implements Builder<MapTree<E>> {
 	private static final long serialVersionUID = 1L;
 
-	private final MapTree<E> root;
+	private MapTree<E> root;
 	private final Map<E, MapTree<E>> idTreeMap;
 	private boolean isBuild;
 
@@ -69,8 +70,17 @@ public class TreeBuilder<E> implements Builder<MapTree<E>> {
 	 * @param config 配置
 	 */
 	public TreeBuilder(final E rootId, final TreeNodeConfig config) {
-		root = new MapTree<>(config);
-		root.setId(rootId);
+		this(new MapTree<E>(config).setId(rootId));
+	}
+
+	/**
+	 * 构造
+	 *
+	 * @param root 根节点
+	 * @since 5.8.33
+	 */
+	public TreeBuilder(final MapTree<E> root) {
+		this.root = root;
 		this.idTreeMap = new LinkedHashMap<>();
 	}
 
@@ -149,6 +159,41 @@ public class TreeBuilder<E> implements Builder<MapTree<E>> {
 		return this;
 	}
 
+	/**
+	 * 增加节点列表，增加的节点是不带子节点的
+	 *
+	 * @param list       Bean列表
+	 * @param <T>        Bean类型
+	 * @param nodeParser 节点转换器，用于定义一个Bean如何转换为Tree节点
+	 * @return this
+	 */
+	public <T> TreeBuilder<E> append(final Iterable<T> list, final NodeParser<T, E> nodeParser) {
+		checkBuilt();
+
+		final TreeNodeConfig config = this.root.getConfig();
+		final Iterator<T> iterator = list.iterator();
+		return append(new Iterator<MapTree<E>>() {
+			@Override
+			public boolean hasNext() {
+				return iterator.hasNext();
+			}
+
+			@Override
+			public MapTree<E> next() {
+				final MapTree<E> node = new MapTree<>(config);
+				nodeParser.parse(iterator.next(), node);
+
+				if(ObjUtil.equals(node.getId(), root.getId())){
+					// issue#IAUSHR 如果指定根节点存在，直接复用
+					TreeBuilder.this.root = node;
+					return null;
+				}
+
+				return node;
+			}
+		});
+	}
+
 	/**
 	 * 增加节点列表，增加的节点是不带子节点的
 	 *
@@ -157,9 +202,8 @@ public class TreeBuilder<E> implements Builder<MapTree<E>> {
 	 */
 	public TreeBuilder<E> append(final Iterable<MapTree<E>> trees) {
 		checkBuilt();
-
-		for (final MapTree<E> tree : trees) {
-			this.idTreeMap.put(tree.getId(), tree);
+		if (null != trees) {
+			append(trees.iterator());
 		}
 		return this;
 	}
@@ -167,25 +211,22 @@ public class TreeBuilder<E> implements Builder<MapTree<E>> {
 	/**
 	 * 增加节点列表，增加的节点是不带子节点的
 	 *
-	 * @param list       Bean列表
-	 * @param <T>        Bean类型
-	 * @param nodeParser 节点转换器，用于定义一个Bean如何转换为Tree节点
+	 * @param iterator 节点列表
 	 * @return this
 	 */
-	public <T> TreeBuilder<E> append(final List<T> list, final NodeParser<T, E> nodeParser) {
+	public TreeBuilder<E> append(final Iterator<MapTree<E>> iterator) {
 		checkBuilt();
 
-		final TreeNodeConfig config = this.root.getConfig();
-		final Map<E, MapTree<E>> map = new LinkedHashMap<>(list.size(), 1);
-		MapTree<E> node;
-		for (final T t : list) {
-			node = new MapTree<>(config);
-			nodeParser.parse(t, node);
-			map.put(node.getId(), node);
+		MapTree<E> tree;
+		while (iterator.hasNext()) {
+			tree = iterator.next();
+			if(null != tree){
+				this.idTreeMap.put(tree.getId(), tree);
+			}
 		}
-		return append(map);
-	}
 
+		return this;
+	}
 
 	/**
 	 * 重置Builder，实现复用

hutool-core/src/main/java/org/dromara/hutool/core/tree/TreeUtil.java

@@ -41,7 +41,7 @@ public class TreeUtil {
 	 * @return {@link MapTree}
 	 * @since 5.7.2
 	 */
-	public static MapTree<Integer> buildSingle(final List<TreeNode<Integer>> list) {
+	public static MapTree<Integer> buildSingle(final Iterable<TreeNode<Integer>> list) {
 		return buildSingle(list, 0);
 	}
 
@@ -51,7 +51,7 @@ public class TreeUtil {
 	 * @param list 源数据集合
 	 * @return List
 	 */
-	public static List<MapTree<Integer>> build(final List<TreeNode<Integer>> list) {
+	public static List<MapTree<Integer>> build(final Iterable<TreeNode<Integer>> list) {
 		return build(list, 0);
 	}
 
@@ -65,7 +65,7 @@ public class TreeUtil {
 	 * @return {@link MapTree}
 	 * @since 5.7.2
 	 */
-	public static <E> MapTree<E> buildSingle(final List<TreeNode<E>> list, final E parentId) {
+	public static <E> MapTree<E> buildSingle(final Iterable<TreeNode<E>> list, final E parentId) {
 		return buildSingle(list, parentId, TreeNodeConfig.DEFAULT_CONFIG, new DefaultNodeParser<>());
 	}
 
@@ -77,7 +77,7 @@ public class TreeUtil {
 	 * @param parentId 最顶层父id值 一般为 0 之类
 	 * @return List
 	 */
-	public static <E> List<MapTree<E>> build(final List<TreeNode<E>> list, final E parentId) {
+	public static <E> List<MapTree<E>> build(final Iterable<TreeNode<E>> list, final E parentId) {
 		return build(list, parentId, TreeNodeConfig.DEFAULT_CONFIG, new DefaultNodeParser<>());
 	}
 
@@ -93,7 +93,7 @@ public class TreeUtil {
 	 * @return {@link MapTree}
 	 * @since 5.7.2
 	 */
-	public static <T, E> MapTree<E> buildSingle(final List<T> list, final E parentId, final NodeParser<T, E> nodeParser) {
+	public static <T, E> MapTree<E> buildSingle(final Iterable<T> list, final E parentId, final NodeParser<T, E> nodeParser) {
 		return buildSingle(list, parentId, TreeNodeConfig.DEFAULT_CONFIG, nodeParser);
 	}
 
@@ -107,7 +107,7 @@ public class TreeUtil {
 	 * @param nodeParser 转换器
 	 * @return List
 	 */
-	public static <T, E> List<MapTree<E>> build(final List<T> list, final E parentId, final NodeParser<T, E> nodeParser) {
+	public static <T, E> List<MapTree<E>> build(final Iterable<T> list, final E parentId, final NodeParser<T, E> nodeParser) {
 		return build(list, parentId, TreeNodeConfig.DEFAULT_CONFIG, nodeParser);
 	}
 
@@ -122,7 +122,7 @@ public class TreeUtil {
 	 * @param nodeParser     转换器
 	 * @return List
 	 */
-	public static <T, E> List<MapTree<E>> build(final List<T> list, final E rootId, final TreeNodeConfig treeNodeConfig, final NodeParser<T, E> nodeParser) {
+	public static <T, E> List<MapTree<E>> build(final Iterable<T> list, final E rootId, final TreeNodeConfig treeNodeConfig, final NodeParser<T, E> nodeParser) {
 		return buildSingle(list, rootId, treeNodeConfig, nodeParser).getChildren();
 	}
 
@@ -139,7 +139,7 @@ public class TreeUtil {
 	 * @return {@link MapTree}
 	 * @since 5.7.2
 	 */
-	public static <T, E> MapTree<E> buildSingle(final List<T> list, final E rootId, final TreeNodeConfig treeNodeConfig, final NodeParser<T, E> nodeParser) {
+	public static <T, E> MapTree<E> buildSingle(final Iterable<T> list, final E rootId, final TreeNodeConfig treeNodeConfig, final NodeParser<T, E> nodeParser) {
 		return TreeBuilder.of(rootId, treeNodeConfig)
 				.append(list, nodeParser).build();
 	}

hutool-core/src/test/java/org/dromara/hutool/core/tree/IssueIAUSHRTest.java

@@ -0,0 +1,58 @@
+package org.dromara.hutool.core.tree;
+
+import lombok.Data;
+import org.dromara.hutool.core.tree.parser.NodeParser;
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class IssueIAUSHRTest {
+	@Test
+	void buildSingleTest() {
+		final List<TestDept> list= new ArrayList<>();
+		TestDept sysDept = new TestDept();
+		sysDept.setDeptId(1L);
+		sysDept.setDeptName("A");
+		sysDept.setParentId(null);
+		list.add(sysDept);
+
+		sysDept = new TestDept();
+		sysDept.setDeptId(2L);
+		sysDept.setDeptName("B");
+		sysDept.setParentId(1L);
+		list.add(sysDept);
+
+		sysDept = new TestDept();
+		sysDept.setDeptId(3L);
+		sysDept.setDeptName("C");
+		sysDept.setParentId(1L);
+		list.add(sysDept);
+
+		final TreeNodeConfig treeNodeConfig = new TreeNodeConfig();
+		treeNodeConfig.setIdKey("deptId");
+		treeNodeConfig.setNameKey("deptName");
+		treeNodeConfig.setParentIdKey("parentId");
+
+		final NodeParser<TestDept,Long> nodeParser= (dept, tree) ->
+			tree.setId(dept.getDeptId())
+				.setParentId(dept.getParentId())
+				.setName(dept.getDeptName());
+
+		final MapTree<Long> longTree = TreeUtil.buildSingle(list, 1L, treeNodeConfig, nodeParser);
+
+		assertEquals("A", longTree.getName());
+		assertEquals(2, longTree.getChildren().size());
+		assertEquals("B", longTree.getChildren().get(0).getName());
+		assertEquals("C", longTree.getChildren().get(1).getName());
+	}
+
+	@Data
+	public static class TestDept {
+		private Long deptId;
+		private String deptName;
+		private Long parentId;
+	}
+}