Java 11 Array of strings to Map of array position, string [duplicate]

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
– Giuseppe Adaldo, Commented Oct 17, 2019 at 9:11

Giuseppe Adaldo · Accepted Answer · 2019-10-16 09:49:37Z

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, 2019 at 9:49

Giuseppe Adaldo

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3 Comments

Naman Over a year ago

.....mapToObj(i -> Map.entry(i + 1, strings[i])) in Java-9 above..though not necessarily required

Holger Over a year ago

Or without boxing overhead, IntStream.range(0, strings.length) .collect(HashMap::new, (m,i) -> m.put(i+1, strings[i]), Map::putAll)

Giuseppe Adaldo Over a year ago

Oh great, this is a more elegant solution

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