java8 建立樹結構的數據

private List<TreeNode> createTree(Integer pid, Map<Integer, List<SysPermission>> map){
    return Optional.ofNullable(map.get(pid)).orElseGet(()->new ArrayList<SysPermission>()).stream().filter(x->x.getParentId() == pid).sorted((x,y)->{return x.getSortNo().compareTo(y.getSortNo());}).map(x->{
        return new TreeNode(x.getRecId(), x.getParentId(), x.getPermissionName(), x.getIcon(), createTree(x.getRecId(), map));
    }).collect(Collectors.toList());
}

private List<TreeNode> getTree(boolean onlyModule){
    EntityWrapper<SysPermission> entityWrapper = new EntityWrapper<>();
    entityWrapper.where("data_status>0");
    if (onlyModule){
        entityWrapper.eq("permission_type", PermissionType.MODULE.getValue());
    }
    entityWrapper.orderBy("sort_no");
    List<SysPermission> list = selectList(entityWrapper);
    return createTree(0, list.stream().collect(groupingBy(SysPermission::getParentId)));
}

TreeNode的定義：

public class TreeNode {    private static final long serialVersionUID = 1L;    private Integer recId;    private Integer pid;    private String nodeName;    private String icon;    private List<TreeNode> children;    public TreeNode(Integer recId, Integer pid, String nodeName, String icon) {        this.recId = recId;        this.pid = pid;        this.nodeName = nodeName;        this.icon = icon;        this.children = new ArrayList<TreeNode>();    }    public TreeNode(Integer recId, Integer pid, String nodeName, String icon, List<TreeNode> children) {        this.recId = recId;        this.pid = pid;        this.nodeName = nodeName;        this.icon = icon;        this.children = children;    }    public Integer getRecId() {        return recId;    }    public void setRecId(Integer recId) {        this.recId = recId;    }    public Integer getPid() {        return pid;    }    public void setPid(Integer pid) {        this.pid = pid;    }    public String getNodeName() {        return nodeName;    }    public void setNodeName(String nodeName) {        this.nodeName = nodeName;    }    public String getIcon() {        return icon;    }    public void setIcon(String icon) {        this.icon = icon;    }    public List<TreeNode> getChildren() {        return children;    }    public void setChildren(List<TreeNode> children) {        this.children = children;    }}