How to split an array into multiple subarrays of size n in java [duplicate]

Question

I want to split an array of integers into multiple subArrays of size n.How can this be achieved?

I tried using following way but it gives OutOfMemoryError

import java.util.*;

public class SplittingArraysIntoSubArrays {

    public static void main(String[] args) {
        int[] arrr = {1,3,2,5,4,6,8,13};
        List<int[]> arrayList = new ArrayList<>();
        int arrayLength = arrr.length;
        int n =3;
        int counter=1;
        
        while(n*counter<arrayLength) {
            arrayList.add(Arrays.copyOf(arrr, 3));
            counter++;
        }       
        System.out.println("Done");
    }   
}

Below is the output i get

[{1,3,2},{1,3,2}]

Pardon me if I am asking an obvious question, but did you try debugging your code? arrr.length is always going to be greater than 0 (zero), hence your while loop never terminates. — Abra
– Abra, Commented Dec 9, 2024 at 13:14
If you are not familiar with using a debugger, you should learn. One of the key points on that page is Using a debugger is an expected basic skill. — Old Dog Programmer
– Old Dog Programmer, Commented Dec 9, 2024 at 17:46
perfect use case for the new Gatherers#windowFixed Gatherer available in Java 24 - javadoc — user85421
– user85421, Commented Dec 9, 2024 at 18:45

Elliott Frisch · Accepted Answer · 2024-12-09 13:32:48Z

1

You need to keep track of your position in the array arrr. You also need to check that there are 3 elements when you copy the (up to) three elements into a new array. And you need to copy ranges of elements from the array, so Arrays.copyOfRange(int[], int, int) would be more appropriate. Putting that together might look something like,

int[] arrr = { 1, 3, 2, 5, 4, 6, 8, 13 };
List<int[]> arrayList = new ArrayList<>();
for (int i = 0; i < arrr.length; i += 3) {
    int n = Math.min(3, arrr.length - i);
    arrayList.add(Arrays.copyOfRange(arrr, i, i + n));
}
for (int[] arr : arrayList) {
    System.out.println(Arrays.toString(arr));
}
System.out.println("Done");

Which outputs

[1, 3, 2]
[5, 4, 6]
[8, 13]
Done

answered Dec 9, 2024 at 13:32

Elliott Frisch

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