Java 11 Array of strings to Map of array position, string

Question

I have an Array of strings that I want to convert in a Map. Without using AtomicInteger or third party API.

sample:

final String[] strings = new String[]{"Arsenal", "Chelsea", "Liverpool"};

final Map<Integer, String> map = new HashMap<>();
for (int i = 0; i < strings.length; i++) {
    map.put(i, strings[i]);
}

System.out.println(map);

which is the best and concise way to achieve so by using streams API?

I don't think that question is related to this problem at all — Giuseppe Adaldo, Oct 17 '19 at 09:11

score 0 · Answer 1 · answered Oct 16 '19 at 09:49

0

After looking into it I found 2 possible solutions:

final Map<Integer, String> map = IntStream.rangeClosed(0, strings.length - 1)
        .mapToObj(i -> new SimpleEntry<>(i + 1, strings[i]))
        .collect(Collectors.toMap(SimpleEntry::getKey, SimpleEntry::getValue));

And:

final Map<Integer, String> map = IntStream.rangeClosed(0, strings.length - 1)
        .boxed()
        .collect(toMap(i -> i + 1, i -> strings[i]));

Where I don't need to instantiate AbstractMap.SimpleEntry

Any better solution? Is there any advice on which one is the best way?

answered Oct 16 '19 at 09:49

Giuseppe Adaldo

295
3
16

....`.mapToObj(i -> Map.entry(i + 1, strings[i]))` in Java-9 above..though not necessarily required – Naman Oct 16 '19 at 13:52
1

Or without boxing overhead, `IntStream.range(0, strings.length) .collect(HashMap::new, (m,i) -> m.put(i+1, strings[i]), Map::putAll)` – Holger Oct 23 '19 at 15:59
Oh great, this is a more elegant solution – Giuseppe Adaldo Oct 24 '19 at 16:19

Java 11 Array of strings to Map of array position, string

1 Answers1