Android : Upload and download file to Amazon from android application

I want to download and upload file to amazon from my android application. I have downloaded AWS SDK and added aws-android-sdk-2.1.5-s3.jar to my build path but not finding some classes to import. below is my code -

AWSCredentials myCredentials = new BasicAWSCredentials(
String.valueOf(Constants.act), String.valueOf(Constants.sk)); 
AmazonS3Client s3Client = new AmazonS3Client(myCredentials);        
S3Object object = s3Client.getObject(new GetObjectRequest("bucket", "file"));

in which i am not able to import - Constants.act and Constants.sk so which jar to use for doing so.

Please help and provide your suggestions. Thanks in advance