轻松编写高效工具类：构建树形结构的秘籍

package com.zking.util;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class BuildTree {
  /**
   * 默认-1为顶级节点
   * @param nodes
   * @param <T>
   * @return
   */
  public static <T> TreeVo<T> build(List<TreeVo<T>> nodes) {
    // 如果节点列表为空，则返回 null
    if (nodes == null) {
      return null;
    }
    // 创建一个空的顶级节点列表
    List<TreeVo<T>> topNodes = new ArrayList<TreeVo<T>>();
    for (TreeVo<T> children : nodes) {
      String pid = children.getParentId();
      // 如果父节点ID为null或者"-1"，则将当前节点视为顶级节点，添加到顶级节点列表中
      if (pid == null || "-1".equals(pid)) {
        topNodes.add(children);
        continue;
      }
      // 遍历节点列表，将当前节点添加到对应的父节点的子节点列表中
      for (TreeVo<T> parent : nodes) {
        String id = parent.getId();
        if (id != null && id.equals(pid)) {
          parent.getChildren().add(children);
          children.setHasParent(true);
          parent.setChildren(true);
          continue;
        }
      }
    }
    TreeVo<T> root = new TreeVo<T>();
    // 根据顶级节点列表的大小决定返回结果
    if (topNodes.size() == 1) {
      // 如果顶级节点列表只有一个节点，将其作为根节点返回
      root = topNodes.get(0);
    } else {
      // 如果顶级节点列表为空或包含多个节点，创建一个虚拟的根节点，将顶级节点列表作为其子节点，然后返回根节点
      root.setId("000");
      root.setParentId("-1");
      root.setHasParent(false);
      root.setChildren(true);
      root.setChecked(true);
      root.setChildren(topNodes);
      root.setText("顶级节点");
      Map<String, Object> state = new HashMap<>(16);
      state.put("opened", true);
      root.setState(state);
    }
    return root;
  }
  /**
   * 指定idParam为顶级节点
   * @param nodes
   * @param idParam
   * @param <T>
   * @return
   */
  public static <T> List<TreeVo<T>> buildList(List<TreeVo<T>> nodes, String idParam) {
    // 如果节点列表为空，则返回 null
    if (nodes == null) {
      return null;
    }
    // 创建一个空的顶级节点列表
    List<TreeVo<T>> topNodes = new ArrayList<TreeVo<T>>();
    for (TreeVo<T> children : nodes) {
      String pid = children.getParentId();
      // 如果父节点ID为null或与idParam相等，则将当前节点视为顶级节点，添加到顶级节点列表中
      if (pid == null || idParam.equals(pid)) {
        topNodes.add(children);
        continue;
      }
      // 遍历节点列表，将当前节点添加到对应的父节点的子节点列表中
      for (TreeVo<T> parent : nodes) {
        String id = parent.getId();
        if (id != null && id.equals(pid)) {
          parent.getChildren().add(children);
          children.setHasParent(true);
          parent.setChildren(true);
          continue;
        }
      }
    }
    return topNodes;
  }
}

package com.zking.util;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
public class TreeVo<T> {
  /**
   * 节点ID
   */
  private String id;
  /**
   * 显示节点文本
   */
  private String text;
  /**
   * 节点状态，open closed
   */
  private Map<String, Object> state;
  /**
   * 节点是否被选中 true false
   */
  private boolean checked = false;
  /**
   * 节点属性
   */
  private Map<String, Object> attributes;
  /**
   * 节点的子节点
   */
  private List<TreeVo<T>> children = new ArrayList<TreeVo<T>>();
  /**
   * 父ID
   */
  private String parentId;
  /**
   * 是否有父节点
   */
  private boolean hasParent = false;
  /**
   * 是否有子节点
   */
  private boolean hasChildren = false;
  public String getId() {
    return id;
  }
  public void setId(String id) {
    this.id = id;
  }
  public String getText() {
    return text;
  }
  public void setText(String text) {
    this.text = text;
  }
  public Map<String, Object> getState() {
    return state;
  }
  public void setState(Map<String, Object> state) {
    this.state = state;
  }
  public boolean isChecked() {
    return checked;
  }
  public void setChecked(boolean checked) {
    this.checked = checked;
  }
  public Map<String, Object> getAttributes() {
    return attributes;
  }
  public void setAttributes(Map<String, Object> attributes) {
    this.attributes = attributes;
  }
  public List<TreeVo<T>> getChildren() {
    return children;
  }
  public void setChildren(List<TreeVo<T>> children) {
    this.children = children;
  }
  public boolean isHasParent() {
    return hasParent;
  }
  public void setHasParent(boolean isParent) {
    this.hasParent = isParent;
  }
  public boolean isHasChildren() {
    return hasChildren;
  }
  public void setChildren(boolean isChildren) {
    this.hasChildren = isChildren;
  }
  public String getParentId() {
    return parentId;
  }
  public void setParentId(String parentId) {
    this.parentId = parentId;
  }
  public TreeVo(String id, String text, Map<String, Object> state, boolean checked, Map<String, Object> attributes,
                  List<TreeVo<T>> children, boolean isParent, boolean isChildren, String parentID) {
    super();
    this.id = id;
    this.text = text;
    this.state = state;
    this.checked = checked;
    this.attributes = attributes;
    this.children = children;
    this.hasParent = isParent;
    this.hasChildren = isChildren;
    this.parentId = parentID;
  }
  public TreeVo() {
    super();
  }
  @Override
  public String toString() {
    return "TreeVo [id=" + id + ", text=" + text + ", state=" + state + ", checked=" + checked + ", attributes="
        + attributes + ", children=" + children + ", parentId=" + parentId + ", hasParent=" + hasParent
        + ", hasChildren=" + hasChildren + "]";
  }
}