tencent cloud

// Create a TransferManager instance, which is used to call the advanced API later.
TransferManager createTransferManager() {
    // Create a COSClient client, which is the basic instance for accessing the COS service.
    // For the detailed code, see "Simple Operations -> Creating a COSClient instance" on this page.
    COSClient cosClient = createCOSClient();

    // Set the thread pool size. You are advised to set the size of your thread pool to 16 or 32 to maximize network resource utilization if you have sufficient client and COS network resources (for example, by using Tencent Cloud CVM and uploading to COS in the same region).
    // We recommend using a smaller value to avoid timeout due to slow network speed if you are transferring data over a public network with poor bandwidth quality.
    ExecutorService threadPool = Executors.newFixedThreadPool(32);

    // Pass a `threadpool`. Otherwise, a single-thread pool will be generated in `TransferManager` by default.
    TransferManager transferManager = new TransferManager(cosClient, threadPool);

    return transferManager;
}

void shutdownTransferManager(TransferManager transferManager) {
    // If the parameter is set to `true`, the COSClient instance in the TransferManager instance will also be closed at the same time.
    // If the parameter is set to `false`, the COSClient instance in the TransferManager instance will not be closed.
    transferManager.shutdownNow(true);
}

public Download download(final GetObjectRequest getObjectRequest, final File file);

// Before using the advanced API, ensure that the process contains a TransferManager instance. If such an instance does not exist, create one.
// For the detailed code, see "Advanced APIs -> Creating a TransferManager instance" on this page.
TransferManager transferManager = createTransferManager();

// Enter the bucket name in the format of `BucketName-APPID`.
String bucketName = "examplebucket-1250000000";
// Object key, the unique ID of an object in a bucket. For more information, please see [Object Key](https://www.tencentcloud.com/document/product/436/13324).
String key = "exampleobject";
// Local file path
String localFilePath = "/path/to/localFile";
File downloadFile = new File(localFilePath);

GetObjectRequest getObjectRequest = new GetObjectRequest(bucketName, key);
try {
    // Return an asynchronous result `Download`. You can synchronously call `waitForCompletion` to wait for the download to end. If successful, `void` is returned; otherwise, an exception will be reported.
    Download download = transferManager.download(getObjectRequest, downloadFile);
    download.waitForCompletion();
} catch (CosServiceException e) {
    e.printStackTrace();
} catch (CosClientException e) {
    e.printStackTrace();
} catch (InterruptedException e) {
    e.printStackTrace();
}

// After confirming that the process does not use the TransferManager anymore, close it.
// For the detailed code, see "Advanced APIs -> Closing a TransferManager instance" on this page.
shutdownTransferManager(transferManager);