public class ArrayChunk {
    public static void main(String[] args) {
        String[][] chunked = chunkArray("1,2,3,4,5,6,7,8,9".split(","), 2);
        System.out.println("Array with chunk size 2");
        Arrays.stream(chunked).forEach(strings -> System.out.println(String.join(",", strings)));
        chunked = chunkArray("1,2,3,4,5,6,7,8,9".split(","), 3);
        System.out.println("Array with chunk size 3");
        Arrays.stream(chunked).forEach(strings -> System.out.println(String.join(",", strings)));
        chunked = chunkArray("1,2,3,4,5,6,7,8,9".split(","), 4);
        System.out.println("Array with chunk size 4");
        Arrays.stream(chunked).forEach(strings -> System.out.println(String.join(",", strings)));
        chunked = chunkArray("1,2,3,4,5,6,7,8,9".split(","), 5);
        System.out.println("Array with chunk size 5");
        Arrays.stream(chunked).forEach(strings -> System.out.println(String.join(",", strings)));
    }
    private static String[][] chunkArray(String[] array, int chunkSize) {
        int chunkedSize = (int) Math.ceil((double) array.length / chunkSize); // chunked array size
        String[][] chunked = new String[chunkedSize][chunkSize];
        for (int index = 0; index < chunkedSize; index++) {
            String[] chunk = new String[chunkSize]; // small array
            System.arraycopy(array, index * chunkSize, chunk, 0, Math.min(chunkSize, array.length - index * chunkSize));
            chunked[index] = chunk;
        }
        return chunked;
    }
}
Output
Array with chunk size 2
1,2
3,4
5,6
7,8
9,null
Array with chunk size 3
1,2,3
4,5,6
7,8,9
Array with chunk size 4
1,2,3,4
5,6,7,8
9,null,null,null
Array with chunk size 5
1,2,3,4,5
6,7,8,9,null