进度条用于指示上传或下载文件的进度。本文以ossClient.putObject方法为例，介绍如何使用进度条。

以下代码用于演示通过ossClient.putObject上传文件时使用进度条的方法：

public class PutObjectProgressListener implements ProgressListener {
    private long bytesWritten = 0;
    private long totalBytes = -1;
    private boolean succeed = false;

    @Override
    public void progressChanged(ProgressEvent progressEvent) {
        long bytes = progressEvent.getBytes();
        ProgressEventType eventType = progressEvent.getEventType();
        switch (eventType) {
        case TRANSFER_STARTED_EVENT:
            System.out.println("Start to upload......");
            break;
        case REQUEST_CONTENT_LENGTH_EVENT:
            this.totalBytes = bytes;
            System.out.println(this.totalBytes + " bytes in total will be uploaded to OSS");
            break;
        case REQUEST_BYTE_TRANSFER_EVENT:
            this.bytesWritten += bytes;
            if (this.totalBytes != -1) {
                int percent = (int)(this.bytesWritten * 100.0 / this.totalBytes);
                System.out.println(bytes + " bytes have been written at this time, upload progress: " + percent + "%(" + this.bytesWritten + "/" + this.totalBytes + ")");
            } else {
                System.out.println(bytes + " bytes have been written at this time, upload ratio: unknown" + "(" + this.bytesWritten + "/...)");
            }
            break;
        case TRANSFER_COMPLETED_EVENT:
            this.succeed = true;
            System.out.println("Succeed to upload, " + this.bytesWritten + " bytes have been transferred in total");
            break;
        case TRANSFER_FAILED_EVENT:
            System.out.println("Failed to upload, " + this.bytesWritten + " bytes have been transferred");
            break;
        default:
            break;
        }
    }

    public boolean isSucceed() {
        return succeed;
    }

    public static void main(String[] args) {
        // Endpoint以杭州为例，其它Region请按实际情况填写。
        String endpoint = "http://oss-cn-hangzhou.aliyuncs.com";
        // 阿里云主账号AccessKey拥有所有API的访问权限，风险很高。强烈建议您创建并使用RAM账号进行API访问或日常运维，请登录RAM控制台创建RAM账号。
        String accessKeyId = "<yourAccessKeyId>";
        String accessKeySecret = "<yourAccessKeySecret>";
        String bucketName = "<yourBucketName>";
        String objectName = "<yourObjectName>";

        // 创建OSSClient实例。
        OSS ossClient = new OSSClientBuilder().build(endpoint, accessKeyId, accessKeySecret);

        try {
            // 上传文件的同时指定了进度条参数。
            ossClient.putObject(new PutObjectRequest(bucketName, objectName, new File("<yourLocalFile>")).
                    <PutObjectRequest>withProgressListener(new PutObjectProgressListener()));

        } catch (Exception e) {
            e.printStackTrace();
        }
        // 关闭OSSClient。
        ossClient.shutdown();
    }
}

ossClient.putObject、ossClient.getObject、ossClient.uploadPart、ossClient.uploadFile以及ossClient.downloadFile方法均支持进度条功能，使用方法与ossClient.putObject类似。

上传文件时进度条使用方法的完整代码请参见GitHub。