public void setUsernameAttributes(java.util.Collection<String> usernameAttributes) {
        if (usernameAttributes == null) {
            this.usernameAttributes = null;
            return;
        }

        this.usernameAttributes = new java.util.ArrayList<String>(usernameAttributes);
    }
<p>
Specifies whether a user can use an email address or phone number as a username when they sign up.
</p>

@param usernameAttributes
       Specifies whether a user can use an email address or phone number as a username when they sign up.
@see UsernameAttributeType
aws-java-sdk-cognitoidp/src/main/java/com/amazonaws/services/cognitoidp/model/CreateUserPoolRequest.java