public class downloads3 {
    private static String bucketName = "s3-upload-sdk-sample-akiaj6ufcgzvw7yukypa";
    **private static String key        = "__________________________________";**

    public static void main(String[] args) throws IOException {
        AmazonS3 s3Client = new AmazonS3Client(new PropertiesCredentials(
                downloads3.class.getResourceAsStream(
                        "AwsCredentials.properties")));
        try {
            System.out.println("Downloading an object");
            S3Object s3object = s3Client.getObject(new GetObjectRequest(
                    bucketName, key));
            System.out.println("Content-Type: "  + 
                    s3object.getObjectMetadata().getContentType());
            displayTextInputStream(s3object.getObjectContent());

           // Get a range of bytes from an object.

            GetObjectRequest rangeObjectRequest = new GetObjectRequest(
                    bucketName, key);
            rangeObjectRequest.setRange(0, 10);
            S3Object objectPortion = s3Client.getObject(rangeObjectRequest);

            System.out.println("Printing bytes retrieved.");
            displayTextInputStream(objectPortion.getObjectContent());

        } catch (AmazonServiceException ase) {
            System.out.println("Caught an AmazonServiceException, which" +
                    " means your request made it " +
                    "to Amazon S3, but was rejected with an error response" +
                    " for some reason.");
            System.out.println("Error Message:    " + ase.getMessage());
            System.out.println("HTTP Status Code: " + ase.getStatusCode());
            System.out.println("AWS Error Code:   " + ase.getErrorCode());
            System.out.println("Error Type:       " + ase.getErrorType());
            System.out.println("Request ID:       " + ase.getRequestId());
        } catch (AmazonClientException ace) {
            System.out.println("Caught an AmazonClientException, which means"+
                    " the client encountered " +
                    "an internal error while trying to " +
                    "communicate with S3, " +
                    "such as not being able to access the network.");
            System.out.println("Error Message: " + ace.getMessage());
        }
    }

    private static void displayTextInputStream(InputStream input)
    throws IOException {
        // Read one text line at a time and display.
        BufferedReader reader = new BufferedReader(new 
                InputStreamReader(input));
        while (true) {
            String line = reader.readLine();
            if (line == null) break;

            System.out.println("    " + line);
        }
        System.out.println();
    }
}

我尝试使用Java从Amazon S3 bucket下载对象。但似乎不起作用，并不断给我以下所示的错误。输入正确的密钥是什么？访问密钥还是密钥？

Downloading an object
Caught an AmazonServiceException, which means your request made it to Amazon S3, but was rejected with an error response for some reason.
Error Message:    The specified key does not exist.
HTTP Status Code: 404
AWS Error Code:   NoSuchKey
Error Type:       Client
Request ID:       F9548FC068DB1646