Convert Enumeration to a Set/List

java

enumeration-to-set

java-8

best-practices

byAnton Shumikhin·Sep 4, 2024

Shuffle an Enumeration into a List with Collections.list(enumeration). Now, do you want a Set too? Simply instantiate a HashSet with the list you just created.

// Like cluttered cable into a neat roll, here we go!
List<T> list = Collections.list(enumeration);

// Fancy no duplication? Use Set. Yep, that simple!
Set<T> set = new HashSet<>(list);

Stay classy and use Java's Collections for polished data structure transformations.

Exploring alternative pathways

Sometimes, the well-travelled path isn't the most scenic. Let's look at Alternative methods for this conversion.

Got Guava? Seize its power

Guava equips you with Iterators.forEnumeration — a handy tool for this conversion ting. Match it with other Guava gems, like ImmutableSet or Sets, and you're golden.

// Mutable set? Like weather in London? Sure.
Set<T> set = Sets.newHashSet(Iterators.forEnumeration(enumeration));

// Immutable set? Fancy being forever alone...with a Set. Here you go, buddy.
ImmutableSet<T> immutableSet = ImmutableSet.copyOf(Iterators.forEnumeration(enumeration));

Apache Commons Collections. Yeah, that's a thing

-> If it's a big, serious project and you're already using Apache commons-collections, then EnumerationUtils.toList is your guy.

List<T> list = EnumerationUtils.toList(enumeration);

However, if all you need is a simple Enumeration-to-Collection conversion, opting for libraries might be like slicing a banana with a lightsaber.

Emphasizing on EnumSet

Slight deviation: EnumSet.allOf() is for our enum buddies, not Enumerations. Don't get things twisted.

Putting on the performance cap

Got to convert to a Set? Using HashSet is generally the fast lane. But, if your data is sort & search fanatic, befriend TreeSet.

Diving deep: Insights and best practices

Null handling and the thread safety conundrum

Envisage your Enumeration might cough up null elements? 🤔 Select a Set or List implementation that can handle them. Got multiple threads in play? Think about synchronized collections (Oh, Vector, you old relic, or Collections.synchronizedSet).

Honoring the fallen (aka duplicates) and maintaining order

Attention! Sets do not preserve duplicates or order. If these are the VIPs in your party, ensure you RSVP with a List or a LinkedHashSet.

Juggling big datasets

For large datasets, conversion can be like wrestling a bear - heavy on memory. A smarter approach might be to process Enumeration elements one-at-a-time, instead of trying to tame the beast at once.

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