public void setExternalId(String externalId) {
        this.externalId = externalId;
    }
<p>
A unique identifier that is required to identify specific groups within your directory. The users of the group
that you associate have access to your Amazon S3 or Amazon EFS resources over the enabled protocols using
Transfer Family. If you know the group name, you can view the SID values by running the following command using
Windows PowerShell.
</p>
<p>
<code>Get-ADGroup -Filter {samAccountName -like "<i>YourGroupName</i>*"} -Properties * | Select SamAccountName,ObjectSid</code>
</p>
<p>
In that command, replace <i>YourGroupName</i> with the name of your Active Directory group.
</p>
<p>
The regular expression used to validate this parameter is a string of characters consisting of uppercase and
lowercase alphanumeric characters with no spaces. You can also include underscores or any of the following
characters: =,.@:/-
</p>

@param externalId
       A unique identifier that is required to identify specific groups within your directory. The users of the
       group that you associate have access to your Amazon S3 or Amazon EFS resources over the enabled protocols
       using Transfer Family. If you know the group name, you can view the SID values by running the following
       command using Windows PowerShell.</p>
       <p>
       <code>Get-ADGroup -Filter {samAccountName -like "<i>YourGroupName</i>*"} -Properties * | Select SamAccountName,ObjectSid</code>
       </p>
       <p>
       In that command, replace <i>YourGroupName</i> with the name of your Active Directory group.
       </p>
       <p>
       The regular expression used to validate this parameter is a string of characters consisting of uppercase
       and lowercase alphanumeric characters with no spaces. You can also include underscores or any of the
       following characters: =,.@:/-
aws-java-sdk-transfer/src/main/java/com/amazonaws/services/transfer/model/UpdateAccessRequest.java