I got this error while getting the list of buckets in Amazon S3 . I know there is already a toolkit available but just wanted to make this simple .  Getting an error Error: Compile Error: Invalid type: S3.AmazonS3 at line 12 column 12 . 

I'm really stucked here . Please help.

 Apex class

public class testAWS_S3_Controller {

    public String getAllBuckets() {
        return null;
    }
    
    public testAWS_S3_Controller() {}

    private String AWSCredentialName = 'Demo_S3_account'; //Modify this string variable to be the name of the AWS Credential record that contains the proper AWS keys and secret
    public String OwnerId {get;set;}
    public String S3Key {get;set;}
    public S3.AmazonS3 as3 {get; private set;} //This object represents an instance of the Amazon S3 toolkit and makes all the Web Service calls to AWS. 
    public S3.ListBucketResult listbucket {get;set;}
    public S3.ListBucketResult ListAllMyBuckets {get;set;}
    
    
    public class AmazonS3 {
        public AmazonS3(String key, String secret){
            this.key = key;
            this.secret= secret;    
        }
        
        public AmazonS3(){
            
        }
   //Method to return a string array for all the buckets in your AWS S3 account
    public String[] allBuckets {
        get {
            try {

                Datetime now = Datetime.now();

                //This performs the Web Service call to Amazon S3 and retrieves all the Buckets in your AWS Account. 
                S3.ListAllMyBucketsResult allBuckets = as3.ListAllMyBuckets(as3.key, now, as3.signature('ListAllMyBuckets', now));

                System.debug(allBuckets);

                //Store the Canonical User Id for your account
                OwnerId = allBuckets.Owner.Id;

                S3.ListAllMyBucketsList bucketList = allBuckets.Buckets;
                S3.ListAllMyBucketsEntry[] buckets = bucketList.Bucket;
                allBucketList = buckets;

                String[] bucketNames = new String[] {};


                //Loop through each bucket entry to get the bucket name and store in string array. 
                for (S3.ListAllMyBucketsEntry bucket: buckets) {
                    System.debug('Found bucket with name: ' + bucket.Name);

                    bucketNames.add(bucket.name);

                }

                return bucketNames;

            } catch (System.NullPointerException e) {
                return null;
            } catch (Exception ex) {
                //System.debug(ex);
                System.debug('caught exception in listallmybuckets');
                ApexPages.addMessages(ex);
                return null;
            }

        } //end getter
        set;
      }
   } 
   
 }

VF page

<apex:page controller="testAWS_S3_Controller">
<apex:outputPanel id="fullRefreshPageId">
<apex:form >

<br/>
<apex:pageBlock title="Force.com for Amazon Web Services">
<apex:pageMessages />

<!--  THIS PAGE BLOCK SECTION ILLUSTRATES HOW TO LIST ALL BUCKETS IN YOUR S3 ACCOUNT -->
<apex:pageBlockSection columns="1" title="List all Buckets in my S3 Account">

<apex:outputText value="Here is the list of buckets available in your S3 account." />
<apex:outputText value="This list is generated by the ListAllMyBuckets web service" />

<apex:dataList value="{!allBuckets}" var="bucket" id="theList">
        <apex:outputText value="{!bucket}"/>
</apex:dataList>
 </apex:pageBlockSection> 

   </apex:pageblock>   
  </apex:form>
    </apex:outputPanel>
  
</apex:page>

Thank you !