求高手帮忙把C#代码转成JAVA代码

if (Request["test_cancel"] == "1") {
                // 保留3秒，测试取消功能，因为本地上传太快了，所以在这模拟一下
                System.Threading.Thread.Sleep(3000);
            }            bool success = false;
            // 这里只是简单的直接保存到 UploadFiles 目录
            if (Request.Files.Count > 0) {                string ext = System.IO.Path.GetExtension(Request.Files[0].FileName).ToLower();
                if (ext == ".jpg" || ext == ".gif" || ext == ".png" && Request.Files[0].ContentLength <= 512 * 1024 * 1024) {
                    
                    success = true;
                    string fileName = Guid.NewGuid().ToString("N") + ext;
                    
                    Request.Files[0].SaveAs(Server.MapPath("~/UploadFiles/") + fileName);
                    
                    Response.Write("{ success: true, fileUrl:'UploadFiles/" + fileName + "' }");
                    Response.End();
                }
            }            if (!success) {
                Response.Write("{ success: false, fileUrl:'' }");
                Response.End();
            }