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Asked: 2026-05-26T20:37:42+00:00

I am retrieving a List from a JPA query, ordered by effectiveDate. There could

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I am retrieving a List from a JPA query, ordered by effectiveDate. There could be duplicate entries except for the date column, and I’ll be ordering them most recent date first (desc). All I want in the set are all the entries with the newest effectiveDate; dupes with older effectiveDates are not allowed in the Set.

If I create a HashSet by passing this List into the constructor, does the new Set only contain the first entries in the List, only the ones with the “newest” effectiveDates?

In other words, are Sets initialized in List order when they are created from a List?

Thanks!

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1 Answer

  1. Editorial Team

    If you create a HashSet from a collection with duplicates, only the first of each duplicate will be added to the hashset.

    It adds the items in the list in order, and the add method does not overwrite duplicates.

    Although this behavior is not specified, it’s highly unlikely to change.

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