JAVA 通用树形结构数据构建工具类

TreeNode

import io.swagger.annotations.ApiModelProperty;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

/**
 * 树结构
 */
@Data
@NoArgsConstructor
public class TreeNode implements Serializable {
    private static final long serialVersionUID = -1506101868495287822L;

    @ApiModelProperty(value = "节点Id")
    private String id;

    @ApiModelProperty(value = "节点名")
    private String label;

    @ApiModelProperty(value = "父节点Id")
    private String parentId;

    @ApiModelProperty(value = "子节点列表")
    private List<TreeNode> children = new ArrayList<>();
}

第一种：单一实体

实现

/**
 * 根据列表，构建树结构
 *
 * @param list 					列表
 * @param rootParentId 	根节点的 parentId
 * @return 树结构数据
 */
public static List<TreeNode> convert(List<TreeNode> list, String rootParentId) {
  List<TreeNode> tree = new ArrayList<>();
  Iterator<TreeNode> iterator = list.iterator();
  while (iterator.hasNext()) {
    TreeNode node = iterator.next();
    String parentId = node.getParentId();
    if (ObjectUtils.isEmpty(parentId) || rootParentId.equals(parentId)) {
      tree.add(node);
      iterator.remove();
    }
  }

  for (TreeNode node : tree) {
    List<TreeNode> children = TreeNode.getChildren(node, list);
    node.getChildren().addAll(children);
  }
  return tree;
}

/**
 * 获取子节点数据
 *
 * @param parentNode 父节点
 * @param list       所有节点集合
 * @return 返回子节点列表
 */
private static List<TreeNode> getChildren(TreeNode parentNode, List<TreeNode> list) {
  List<TreeNode> children = new ArrayList<>();
  Iterator<TreeNode> iterator = list.iterator();
  while (iterator.hasNext()) {
    TreeNode node = iterator.next();
    // 如果当前节点 ID 与父节点 ID 一致，表示当前数据是该节点的子节点
    if (parentNode.getId().equals(node.getParentId())) {
      children.add(node);
      iterator.remove();
    }
  }
  // 递归调用
  for (TreeNode node : children) {
    // 调用自身方法，依次添加子节点数据
    node.getChildren().addAll(getChildren(node, list));
  }
  return children;
}

使用例子

List<TreeNode> list = new ArrayList<>();
list.add(...);
...

// 构建树形结构数据
List<TreeNode> tree = convert(list, "-1");

第二种：任意实体

实现

public class TreeUtils {
    /**
     * 根据列表，构建树结构
     *
     * @param list                列表
     * @param getIdFunction       Id
     * @param getParentIdFunction parentId
     * @param setChildrenFunction children 列表
     * @param rootParentId        跟节点父级 ID，一般为 0 或 -1
     * @return 树结构数据
     */
    public static <T> List<T> build(
            List<T> list,
            Function<T, ?> getIdFunction,
            Function<T, ?> getParentIdFunction,
            BiConsumer<T, List<T>> setChildrenFunction,
            Long rootParentId
    ) {
        List<T> tree = new ArrayList<>();
        Iterator<T> iterator = list.iterator();
        while (iterator.hasNext()) {
            T node = iterator.next();
            Object parentId = getParentIdFunction.apply(node);
            if (ObjectUtils.isEmpty(parentId) || rootParentId.equals(parentId)) {
                tree.add(node);
                iterator.remove();
            }
        }

        for (T node : tree) {
            List<T> children = getChildren(node, list, getIdFunction, getParentIdFunction, setChildrenFunction);
            if (!children.isEmpty()) {
                setChildrenFunction.accept(node, children);
            }
        }
        return tree;
    }

    /**
     * 获取子节点数据
     *
     * @param parentNode 父节点
     * @param list       所有节点集合
     * @return 返回子节点列表
     */
    private static <T> List<T> getChildren(
            T parentNode,
            List<T> list,
            Function<T, ?> getIdFunction,
            Function<T, ?> getParentFunction,
            BiConsumer<T, List<T>> setChildrenFunction
    ) {
        List<T> children = new ArrayList<>();
        Iterator<T> iterator = list.iterator();
        while (iterator.hasNext()) {
            T node = iterator.next();
            // 如果当前节点 ID 与父节点 ID 一致，表示当前数据是该节点的子节点
            Object id = getIdFunction.apply(parentNode);
            Object parentId = getParentFunction.apply(node);
            if (id.toString().equals(parentId.toString())) {
                children.add(node);
                iterator.remove();
            }
        }
        // 递归调用
        for (T node : children) {
            // 调用自身方法，依次添加子节点数据
            List<T> childrenNodes = getChildren(node, list, getIdFunction, getParentFunction, setChildrenFunction);
            if (!childrenNodes.isEmpty()) {
                setChildrenFunction.accept(node, childrenNodes);
            }
        }
        return children;
    }
}

使用例子

List<TreeNode> list = new ArrayList<>();
list.add(...);
...

// 构建树形结构数据
List<TreeNode> tree = build(list, TreeNode::getId, TreeNode::getParentId, TreeNode::setChildren, "-1");