public MasterUserOptions withMasterUserName(String masterUserName) {
        setMasterUserName(masterUserName);
        return this;
    }
<p>
User name for the master user. Only specify if <code>InternalUserDatabaseEnabled</code> is <code>true</code>.
</p>

@param masterUserName
       User name for the master user. Only specify if <code>InternalUserDatabaseEnabled</code> is
       <code>true</code>.
@return Returns a reference to this object so that method calls can be chained together.
aws-java-sdk-opensearch/src/main/java/com/amazonaws/services/opensearch/model/MasterUserOptions.java