public String getUserPoolId() {
        return this.userPoolId;
    }
<p>
The ID of the user pool that is associated with the custom domain whose certificate you're updating.
</p>

@return The ID of the user pool that is associated with the custom domain whose certificate you're updating.
aws-java-sdk-cognitoidp/src/main/java/com/amazonaws/services/cognitoidp/model/UpdateUserPoolDomainRequest.java