public String getIdempotencyToken() {
        return this.idempotencyToken;
    }
<p>
Customer chosen string that can be used to distinguish between calls to <code>RequestCertificate</code>.
Idempotency tokens time out after one hour. Therefore, if you call <code>RequestCertificate</code> multiple times
with the same idempotency token within one hour, ACM recognizes that you are requesting only one certificate and
will issue only one. If you change the idempotency token for each call, ACM recognizes that you are requesting
multiple certificates.
</p>

@return Customer chosen string that can be used to distinguish between calls to <code>RequestCertificate</code>.
        Idempotency tokens time out after one hour. Therefore, if you call <code>RequestCertificate</code>
        multiple times with the same idempotency token within one hour, ACM recognizes that you are requesting
        only one certificate and will issue only one. If you change the idempotency token for each call, ACM
        recognizes that you are requesting multiple certificates.
aws-java-sdk-acm/src/main/java/com/amazonaws/services/certificatemanager/model/RequestCertificateRequest.java