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

        this.userNames = new java.util.ArrayList<String>(userNames);
    }
<p>
The list of user names that belong to the ACL.
</p>

@param userNames
       The list of user names that belong to the ACL.
aws-java-sdk-memorydb/src/main/java/com/amazonaws/services/memorydb/model/ACL.java