Modelling associations to Java Enums in UML Class diagrams
<p>I am confused about the usage of associations with Java Enums in UML Class diagrams.
Currently I am modelling a system containing a <em>Car</em> class that has some properties. Some are also Enums, just like <em>FuelKind</em> or <em>CarBrand</em>:</p>

<p><a href="https://i.stack.imgur.com/WpViM.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/WpViM.png" alt="enter image description here"></a></p>

<p>There are going to be a lot of cars in the database (<em>Car</em> is a JPA entity) and I'm asking myself which is the best association and cardinality to <em>FuelKind</em> and <em>CarBrand</em>.</p>

<p>My thoughts until now:</p>

<ul>
<li>Enum instances are instantiated on their own, so technically they do not depend on <em>Car</em>. Also non-technically those enums contain all available 'choices', so there is no strict dependency. So it can not be a Composition Aggregation between them.</li>
<li>One <em>Car</em> has one <em>CarBrand</em> and one <em>FuelKind</em>. But from the other side: Does one brand or fuel kind have one car or multiple cars? Logically multiple cars can be from Mercedes or driving on petrol. But technically a enum instance has no link to one or multiple cars.</li>
</ul>

<p>Do you have some suggestions and thoughts on how to solve this problem?</p>