public Boolean getPerformCheckOnly() {
        return this.performCheckOnly;
    }
<p>
This flag, when set to True, indicates that an Upgrade Eligibility Check needs to be performed. This will not
actually perform the Upgrade.
</p>

@return This flag, when set to True, indicates that an Upgrade Eligibility Check needs to be performed. This will
        not actually perform the Upgrade.
aws-java-sdk-elasticsearch/src/main/java/com/amazonaws/services/elasticsearch/model/UpgradeElasticsearchDomainRequest.java