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    <p>Like your own question suggests, <strong>the key is the domain, not JPA</strong>. JPA is just a framework which you can (and should) use in a way which best fits your problem. Choosing a suboptimal solution because of framework (or its limits) is usually a warning bell.</p> <p>When I need a set and never care about order, I use a <code>Set</code>. When for some reason order is important (ordered list, ordering by date, etc.), then a <code>List</code>.</p> <p>You seem to be well aware of the difference between <code>Collection</code>, <code>Set</code>, and <code>List</code>. The only reason to use one vs. the other depends only on your needs. You can <strong>use them to communicate to users of your API (or your future self) the properties of your collection</strong> (which may be subtle or implicit). </p> <p>This is follows the exact same rules as using different collection types anywhere else throughout your code. You could use <code>Object</code> or <code>Collections</code> for all your references, yet in most cases you use more concrete types.</p> <p>For example, when I see a <code>List</code>, I know it comes sorted in some way, and that duplicates are either acceptable or irrelevant for this case. When I see a <code>Set</code>, I usually expect it to have no duplicates and no specific order (unless it's a <code>SortedSet</code>). When I see a <code>Collection</code>, I don't expect anything more from it than to contain some entities.</p> <p>Regarding list ordering... Yes, it can be preserved. And even if it's not and you just use <code>@OrderBy</code>, it still can be useful. Think about the example of event log sorted by timestamp by default. Artificially reordering the list makes little sense, but still it can be useful that it comes sorted by default.</p>
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    1. POWhich Java Type do you use for JPA collections and why?
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    1. USKonrad Garus
    1. USKonrad Garus
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    1. POWhich Java Type do you use for JPA collections and why?
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    1. COShouldn't you end up always using `Set` then? Because you are storing your entities in a relational database, where there can't be any duplicate elements and where you have to define an order by yourself (i.e. the order in you Java `List` is not preserved when it is persisted). And when do you use `Collection`?
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    2. COIf necessary, you can persist `List` order using an artificial field. In most cases, though, it is natural. One example can be some kind of a time-based log, where you can use @OrderBy("eventDate"). As for `Collection`, I would use it in similar situations as `Set`.
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    3. COYes, you can use and index column or you can use the `@OrderBy` annotation, but this order specified by these means is not related to order in your Java list. You can also use the `@OrderBy` annotation on a `Set` or use an index column. And if you change the order in your java list, the ordering in the DB will not be reflected in the DB.
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