java8 通用树形菜单工具

工具类

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

/**
 * 
 *
 * @author CJJ
 * @version 1.0
 * @createDate 2020/06/29 9:09
 */
public class TreeUtil {

    /**
     * 空间换时间 将同级list转成树形对象
     *
     * @param list
     * @return
     */
    public synchronized T peerToLevel(List list) {
        //SysConstants.TREE_ROOT_ID 自定义根节点id
        T root = (T) new TreeVo(SysConstants.TREE_ROOT_ID);
        List parentList = list.stream().filter(l -> l.getParentId().equals(root.getId())).collect(Collectors.toList());
        list.removeAll(parentList);
        convert(parentList, list);
        root.getChildren().addAll(parentList);
        return root;
    }

    /**
     * 转换递归
     * @param parentList
     * @param nodeList
     */
    private synchronized void convert(List parentList, List nodeList) {
        List tempParentList = new ArrayList<>();
        List tempNodeList = new ArrayList<>();
        parentList.forEach(parent -> {
            nodeList.forEach(
                    node -> {
                        if (node.getParentId().equals(parent.getId())) {
                            parent.getChildren().add(node);
                            tempNodeList.add(node);
                            tempParentList.add(node);
                        }
                    }
            );

        });
        nodeList.removeAll(tempNodeList);
        if (!nodeList.isEmpty()) {
            convert(tempParentList, nodeList);
        }
    }

    public static void main(String[] args) {
        TreeVo node = new TreeVo("0", "-1", "0");
        TreeVo node1 = new TreeVo("1", "-1", "1");
        TreeVo node2 = new TreeVo("2", "0", "2");
        TreeVo node3 = new TreeVo("3", "0", "3");
        TreeVo node4 = new TreeVo("4", "1", "4");
        TreeVo node5 = new TreeVo("5", "3", "5");
        TreeVo node6 = new TreeVo("6", "4", "6");
        TreeVo node7 = new TreeVo("7", "5", "7");
        TreeVo node8 = new TreeVo("8", "5", "8");
        ArrayList treeVos = new ArrayList<>();
        treeVos.addAll(Arrays.asList(node, node1, node2, node3, node4, node5, node6, node7, node8));


        TreeUtil treeUtil = new TreeUtil<>();
        TreeVo root = treeUtil.peerToLevel(treeVos);
        System.out.println(root.toString());
    }
}

实体类TreeVo

/**
 * 
 *
 * @author CJJ
 * @version 1.0
 * @createDate 2020/06/29 9:04
 */

import lombok.Data;
import lombok.NoArgsConstructor;

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

/**
 * 
 *
 * @author CJJ
 * @version 1.0
 * @createDate 2019/08/30 17:22
 */
@NoArgsConstructor
@Data
public class TreeVo implements Comparable {

    protected String id;
    protected String parentId;
    private String name;
    /**
     * 排序 每一层单独排序
     */
    protected Integer sort;

    protected ArrayList children = new ArrayList<>(

    );

    public TreeVo(String treeRootId) {
        this.id = treeRootId;
    }

    public TreeVo(String id, String parentId, String name) {
        this.id = id;
        this.parentId = parentId;
        this.name = name;
    }

    public void setChildren(ArrayList children) {
        Collections.sort(children);
        this.children = children;
    }


    @Override
    public int compareTo(TreeVo o) {
        return sort.compareTo(o.getSort());
    }
}