Convert Map to array of Integer

Question

Can someone tell me what I am doing wrong here? p.getVote(), and the collection counting logic return a Long, but I am trying to make my end output an array of ints.

Map<Integer, Long> counters = iqr.getQgagueUniqueVotes().stream()
                               .collect(Collectors.groupingBy(p -> ((int)p.getVote()), 
                                    Collectors.counting()));
Collection<Long> values = counters.values();
long[] targetArray = values.toArray(new Long[values.size()]);

Error:

Incompatible type: Inference variable has incompatible upper bound

Is your issue just with converting `Map` to `long[]`? Then you probably should replace the initialisation based on a stream statement (that's also dependent on a variable you didn't show) with some hard-coded data. See also: [mcve]. — Bernhard Barker, Feb 25 '18 at 19:46
Similar: [How to convert an ArrayList containing Integers to primitive int array?](https://stackoverflow.com/q/718554) — Bernhard Barker, Feb 25 '18 at 19:56

score 3 · Accepted Answer · answered Feb 25 '18 at 19:42

3

Change the type of the targetArray array to a type Long:

Long[] targetArray = values.toArray(new Long[values.size()]);

or create a stream of the values and map to a type long then collect to an array.

long[] targetArray = values.stream().mapToLong(Long::longValue).toArray();

answered Feb 25 '18 at 19:42

Ousmane D.

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3

I recommend [this article](https://shipilev.net/blog/2016/arrays-wisdom-ancients/) regarding the pattern of using `.toArray(new Long[values.size()])` instead of `.toArray(new Long[0])`. – Holger Feb 26 '18 at 08:56

Convert Map to array of Integer

1 Answers1