Convert Enumeration to a Set/List

Question

Is there some one-liner bridge method to dump a given Enumeration to java.util.List or java.util.Set?

Something built-in like Arrays.asList() or Collection.toArray() should exist somewhere, but I'm unable to find that in my IntelliJ debugger's evaluator window (and Google/SO results, too).

Counterblast

Answer 1

You can use Collections.list() to convert an Enumeration to a List in one line:

List<T> list = Collections.list(enumeration);

There's no similar method to get a Set, however you can still do it one line:

Set<T> set = new HashSet<T>(Collections.list(enumeration));

Milwaukee

Somehow I missed this method while lurking in the autocompletion dropdown. Thanks! – Counterblast

Answer 2

How about this: Collections.list(Enumeration e) returns an ArrayList<T>

Griseofulvin

Answer 3

If you need Set rather than List, you can use EnumSet.allOf().

Set<EnumerationClass> set = EnumSet.allOf(EnumerationClass.class);

Update: JakeRobb is right. My answer is about java.lang.Enum instead of java.util.Enumeration. Sorry for unrelated answer.

Beady

I'm pretty sure the asker was asking about java.util.Enumeration, the legacy cousin of Iterator, not java.lang.Enum, the thing you get when you use the 'enum' keyword. – Sapiential

I did a google search for "java convert enum into a set" and this thread came back as the first response. @Timur gets my upvote. – Coed

Answer 4

When using guava (See doc) there is Iterators.forEnumeration. Given an Enumeration x you can do the following:

to get a immutable Set:

ImmutableSet.copyOf(Iterators.forEnumeration(x));

to get a immutable List:

ImmutableList.copyOf(Iterators.forEnumeration(x));

to get a hashSet:

Sets.newHashSet(Iterators.forEnumeration(x));

Woodie

Answer 5

There's also in Apache commons-collections EnumerationUtils.toList(enumeration)

Mascle

Answer 6

I needed same thing and this solution work fine, hope it can help someone also

Enumeration[] array = Enumeration.values();
List<Enumeration> list = Arrays.asList(array);

then you can get the .name() of your enumeration.

Middlings

Your answer shows how to convert an array into a list and it only happens that you have an array of Enumerations. The question was about Enumeration->List conversion. – Gagnon