lambda表达式将List对象某个字段转换以逗号分隔的String类型

 StringBuffer sb = new StringBuffer();
        //获取节点id
        list.forEach(ztree -> {
            if (!(infoParentId.equals((ztree.getpId())))) {
                sb.append(ztree.getId()).append(",");
            }
        });
        sb.deleteCharAt(sb.length() - 1);
        String str = sb.toString();