Convert String to int array in Java the fast way

Question

does anyone know a faster way to convert string to int array?

Java V7

The format given is "4 343 234 -24" and so on. Spaces between the numbers, amount of numbers is known beforhand just as is the range within the numbers are

long[] array = new long[length];            
for (int i = 0; i < length - 1; i++) {
    array[i] = Integer.parseInt(n.substring(0, n.indexOf(' ')));
    n = n.substring(n.substring(0, n.indexOf(' ')).length() + 1);
}
array[length - 1] = Integer.parseInt(n);

If it is working already better you post it on codereview.stackexchange.com — Suresh Atta, Dec 21 '17 at 12:41
try splitting the input string into the component numbers then converting each of those to a long/int as appropriate — AdamPillingTech, Dec 21 '17 at 12:41
Just use `String#split` that will split your string depending of a delimiter (use " " here), and you get an array of all different numbers. — Turtle, Dec 21 '17 at 12:42
I'm voting to close this question as off-topic because questions asking to review working code belong on codereview.stackexchange.com — GhostCat, Dec 21 '17 at 12:48

ItamarG3 · Accepted Answer · 2017-12-21T13:05:30.343

1

Using String.split() is by far the most efficient when you want to split by a single character (a space, in your case).

If you are aiming for maximal efficiency when splitting by spaces, then this would be a good solution:

List<Integer> res = new ArrayList<>();
Arrays.asList(kraft.split(" ")).forEach(s->res.add(Integer.parseInt(s)));
Integer[] result = res.toArray(new Integer[0]);

And this works for any number of numbers.

edited Dec 21 '17 at 13:05

answered Dec 21 '17 at 12:53

ItamarG3

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@MelissaLoos then hold on one moment. (`List` has some method for converting it to an array, I just can't remember it by heart) – ItamarG3 Dec 21 '17 at 13:03
@ItamarG3 You could add the parsed `int`s directly to an array. – Turtle Dec 21 '17 at 13:11
@Nathan i felt this is more elegant. Not sure why – ItamarG3 Dec 21 '17 at 13:13
@MelissaLoos `Integer` is an object class representing an `int`. Same for `Long` and `long`. You can replace `Integer[] result` by `int[]`. – Turtle Dec 21 '17 at 13:17
There is no need for the intermediate `List`. – senjin.hajrulahovic Nov 04 '18 at 19:30
@senjin.hajrulahovic you're right, but this way it's clear to the reader what's going on, what the types are and how this works... – ItamarG3 Nov 05 '18 at 10:08

Deepesh Kumar · Answer 2 · 2018-11-07T07:34:29.893

0

if You are using Java8 or higher version then you can get your expected output by writing this single line of code.

String str= "4 343 234 -24";

int[] intArr=Stream.of(str.split(" ")).mapToInt(Integer::parseInt).toArray();

System.out.println(Arrays.toString(intArr));

edited Nov 07 '18 at 07:34

answered Nov 03 '18 at 21:07

Deepesh Kumar

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Why the `str1.replace("-", "")`? The question does not mention absolute values. – senjin.hajrulahovic Nov 04 '18 at 20:44
1

Check the Updated Code now. l already fixed that by removing The replace() method. – Deepesh Kumar Nov 07 '18 at 07:35

senjin.hajrulahovic · Answer 3 · 2018-11-04T22:02:00.180

0

Splitting the input with the pattern \\s+ would handle one or more white-space characters, not only spaces, appearing between the numbers.

Stream.of(input.split("\\s+")).mapToInt(Integer::parseInt).toArray();

The mapToInt method returns an IntStream which provides the toArray method. This method returns an array containing the elements of the IntStream.

edited Nov 04 '18 at 22:02

answered Nov 04 '18 at 19:27

senjin.hajrulahovic

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Convert String to int array in Java the fast way

3 Answers3