问COS如何用SDK进行批量上传？

怎么批量上传文件，我用SDK循环上传，但是会报错FATAL EXCEPTION: session_pooljava.util.ConcurrentModificationExceptionat java.util.ArrayList$ArrayListIterator.next(ArrayList.java:573)at com.tencent.upload.task.storage.StorageHelper.saveUploadTasks(Unknown Source)at com.tencent.upload.impl.TaskManager.onTaskInfoChanged(Unknown Source)at com.tencent.upload.impl.SessionManager.saveTaskInfo(Unknown Source)at com.tencent.upload.task.UploadTask.onTaskInfoChanged(Unknown Source)