public String getExternalId() {
        return this.externalId;
    }
<p>
A unique identifier that might be required when you assume a role in another account. If the administrator of the
account to which the role belongs provided you with an external ID, then provide that value in the
<code>ExternalId</code> parameter. This value can be any string, such as a passphrase or account number. A
cross-account role is usually set up to trust everyone in an account. Therefore, the administrator of the
trusting account might send an external ID to the administrator of the trusted account. That way, only someone
with the ID can assume the role, rather than everyone in the account. For more information about the external ID,
see <a href="https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_create_for-user_externalid.html">How to
Use an External ID When Granting Access to Your Amazon Web Services Resources to a Third Party</a> in the <i>IAM
User Guide</i>.
</p>
<p>
The regex used to validate this parameter is a string of characters consisting of upper- and lower-case
alphanumeric characters with no spaces. You can also include underscores or any of the following characters:
=,.@:/-
</p>

@return A unique identifier that might be required when you assume a role in another account. If the
        administrator of the account to which the role belongs provided you with an external ID, then provide
        that value in the <code>ExternalId</code> parameter. This value can be any string, such as a passphrase
        or account number. A cross-account role is usually set up to trust everyone in an account. Therefore, the
        administrator of the trusting account might send an external ID to the administrator of the trusted
        account. That way, only someone with the ID can assume the role, rather than everyone in the account. For
        more information about the external ID, see <a
        href="https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_create_for-user_externalid.html">How to
        Use an External ID When Granting Access to Your Amazon Web Services Resources to a Third Party</a> in the
        <i>IAM User Guide</i>.</p>
        <p>
        The regex used to validate this parameter is a string of characters consisting of upper- and lower-case
        alphanumeric characters with no spaces. You can also include underscores or any of the following
        characters: =,.@:/-
aws-java-sdk-sts/src/main/java/com/amazonaws/services/securitytoken/model/AssumeRoleRequest.java