JAVA树形结构工具类

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BaseTreeObj.java

/**
 * 基层树形结构实体类
 * 必备属性:id,parentId,childsList
 */
@Data
public class BaseTreeObj implements Serializable {
    private static final long serialVersionUID = 1L;
    private String id;
    private String parentId;
    private String name;
    private List<BaseTreeObj> childsList = new ArrayList<>();
}

TreeUtil.java

package com.soyea.tree;

import org.springframework.util.CollectionUtils;

import java.util.ArrayList;
import java.util.List;

/**
 * 获得树形结构的工具类
 * 实际使用,可将BaseTreeObj直接覆盖为指定类
 */
public class TreeUtil {

    /**
     * 获得指定节点下所有归档
     * @param list
     * @param parentId
     * @return
     */
    public static List<BaseTreeObj> list2TreeConverter(List<BaseTreeObj> list, String parentId) {
        List<BaseTreeObj> returnList = new ArrayList<>();

        for (BaseTreeObj res : list) {
            //判断对象是否为根节点
            if (res.getParentId().equals(parentId)) {
                //该节点为根节点,开始递归
                recursionFn(list, res); //通过递归为节点设置childList

                returnList.add(res);
            }
        }

        return returnList;
    }

    /**
     * 递归列表
     * 通过递归,给指定t节点设置childList
     * @param list
     * @param t
     */
    public static void recursionFn(List<BaseTreeObj> list, BaseTreeObj t) {
        //只能获取当前t节点的子节点集,并不是所有子节点集
        List<BaseTreeObj> childsList = getChildList(list, t);
        //设置他的子集对象集
        t.setChildsList(childsList);

        //迭代子集对象集
        for (BaseTreeObj nextChild : childsList) { //遍历完,则退出递归

            //判断子集对象是否还有子节点
            if (!CollectionUtils.isEmpty(childsList)) {
                //有下一个子节点,继续递归
                recursionFn(list, nextChild);
            }
        }
    }   /**
     * 获得指定节点下的所有子节点
     * @param list
     * @param t
     * @return
     */
    public static List<BaseTreeObj> getChildList(List<BaseTreeObj> list, BaseTreeObj t) {
        List<BaseTreeObj> childsList = new ArrayList<BaseTreeObj>();
        //遍历集合元素,如果元素的Parentid==指定元素的id,则说明是该元素的子节点
        for (BaseTreeObj t1 : list) {
            if (t1.getParentId() .equals(t.getId()) ) {
                childsList.add(t1);
            }
        }

        return childsList;
    }   /**
     * 判断是否还有下一个子节点
     * @param list
     * @param t
     */
    public static boolean hasChild(List<BaseTreeObj> list, BaseTreeObj t) {
        return getChildList(list, t).size() > 0 ? true : false;
    }

}

树形工具类

package com.github.wxiaoqi.security.common.util;

import com.github.wxiaoqi.security.common.vo.TreeNode;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by Ace on 2017/6/12.
 */
public class TreeUtil{
  /**
   * 两层循环实现建树
   * 
   * @param treeNodes 传入的树节点列表
   * @return
   */
  public static <T extends TreeNode> List<T> bulid(List<T> treeNodes,Object root) {

    List<T> trees = new ArrayList<T>();

    for (T treeNode : treeNodes) {

      if (root.equals(treeNode.getParentId())) {
        trees.add(treeNode);
      }

      for (T it : treeNodes) {
        if (it.getParentId() == treeNode.getId()) {
          if (treeNode.getChildren() == null) {
            treeNode.setChildren(new ArrayList<TreeNode>());
          }
          treeNode.add(it);
        }
      }
    }
    return trees;
  }

  /**
   * 使用递归方法建树
   * 
   * @param treeNodes
   * @return
   */
  public static <T extends TreeNode> List<T> buildByRecursive(List<T> treeNodes,Object root) {
    List<T> trees = new ArrayList<T>();
    for (T treeNode : treeNodes) {
      if (root.equals(treeNode.getParentId())) {
        trees.add(findChildren(treeNode, treeNodes));
      }
    }
    return trees;
  }

  /**
   * 递归查找子节点
   * 
   * @param treeNodes
   * @return
   */
  public static <T extends TreeNode> T findChildren(T treeNode, List<T> treeNodes) {
    for (T it : treeNodes) {
      if (treeNode.getId() == it.getParentId()) {
        if (treeNode.getChildren() == null) {
          treeNode.setChildren(new ArrayList<TreeNode>());
        }
        treeNode.add(findChildren(it, treeNodes));
      }
    }
    return treeNode;
  }

}package com.github.wxiaoqi.security.common.vo;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by Ace on 2017/6/12.
 */
public class TreeNode {
    protected int id;
    protected int parentId;
    List<TreeNode> children = new ArrayList<TreeNode>();

    public List<TreeNode> getChildren() {
        return children;
    }

    public void setChildren(List<TreeNode> children) {
        this.children = children;
    }
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getParentId() {
        return parentId;
    }

    public void setParentId(int parentId) {
        this.parentId = parentId;
    }

    public void add(TreeNode node){
        children.add(node);
    }
}

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