How to convert Integer[] to int[] array in Java?

Question

Is there a fancy way to cast an Integer array to an int array? (I don't want to iterate over each element; I'm looking for an elegant and quick way to write it)

The other way around I'm using

scaleTests.add(Arrays.stream(data).boxed().toArray(Double[]::new));

I'm looking for an one-liner but wasn't able to find something.

The goal is to:

int[] valuesPrimitives = <somehow cast> Integer[] valuesWrapper

The actual question is: why would you want to do that? The damage has already been dealt (you already created all the `Double` objects and payed with higher execution time and higher memory usage). — Turing85, Jul 13 '15 at 22:44
No you cannot cast it, as a `Double[]` is not a `double[]`. There will be an iteration behind the scenes. A one-liner could be: `double[] valuesPrimitives = Stream.of(valuesWrapper).mapToDouble(d -> d).toArray();` — Alexis C., Jul 13 '15 at 22:44
http://stackoverflow.com/questions/564392/converting-an-array-of-objects-to-an-array-of-their-primitive-types — Andy Turner, Jul 13 '15 at 22:45
@Turing85, might be he just want to improve the code readability. I, as a developer assume that when I get to see huge code written by him, I can get to business logic quickly, rather than spending time on few lines of code which just does conversion part — JavaHopper, Jul 14 '15 at 03:12
@JavaHopper I think you misunderstood me. I see why one wants a short and elegant solution for the conversion. I do not see why one wants the actual conversion. You can simply use the `Double[]` instead of `double[]`. — Turing85, Jul 14 '15 at 06:20

score 78 · Accepted Answer · answered Jul 13 '15 at 22:46

78

You can use Stream APIs of Java 8

int[] intArray = Arrays.stream(array).mapToInt(Integer::intValue).toArray();

answered Jul 13 '15 at 22:46

Vaibhav

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Sometimes I prefer to see `mapToInt(i -> i)`. – Marko Topolnik Jul 14 '15 at 09:25

score 5 · Answer 2 · edited Jul 12 '20 at 07:25

5

If you can consider using Apache commons ArrayUtils then there is a simple toPrimitive API:

public static double[] toPrimitive(Double[] array, double valueForNull)

Converts an array of object Doubles to primitives handling null.

This method returns null for a null input array.

edited Jul 12 '20 at 07:25

Littm

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answered Jul 13 '15 at 22:45

Juned Ahsan

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Hi thanks for the answer. Unfortunately I forgot to mention that I cannot use ArrayUtils. But thanks anyways – Michael Brenndoerfer Jul 13 '15 at 22:47

score 2 · Answer 3 · answered Jul 14 '17 at 17:59

Using Guava, you can do the following:

int[] intArray = Ints.toArray(intList);

If you're using Maven, add this dependency:

<dependency>
   <groudId>com.google.guava</groupId>
   <artifactId>guava</artifactId>
   <version>18.0</version>
</dependency>

Antônio Sérgio Ferraz · Answer 4 · 2019-04-05T14:15:03.390

1

If you have access to the Apache lang library, then you can use the ArrayUtils.toPrimitive(Integer[]) method like this:

int[] primitiveArray = ArrayUtils.toPrimitive(objectArray);

edited Apr 05 '19 at 14:15

answered Oct 05 '18 at 11:46

Antônio Sérgio Ferraz

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score 1 · Answer 5 · edited Feb 06 '20 at 08:19

1

You can download the org.apache.commons.lang3 jar file which provides ArrayUtils class.
Using the below line of code will solve the problem:

ArrayUtils.toPrimitive(Integer[] nonPrimitive)

Where nonPrimitive is the Integer[] to be converted into the int[].

edited Feb 06 '20 at 08:19

Dr.jacky

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answered Feb 06 '20 at 07:46

Shekhar

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How to convert Integer[] to int[] array in Java?

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