return 2D array

public class GroupByRemainder {

    // A method that takes an array of numbers and returns a 2D array of numbers
    // where the first dimension is the remainder of 3 and the second dimension is the list of numbers with that remainder
    public static int[][] groupByRemainder(int[] numbers) {
        // Create an empty 2D array with 3 rows and 0 columns
        int[][] groups = new int[3][0];

        // Loop through the array of numbers
        for (int number : numbers) {
            // Compute the remainder of 3
            int remainder = number % 3;

            // Get the current length of the row corresponding to the remainder
            int length = groups[remainder].length;

            // Create a new array with one more element than the current row
            int[] newRow = new int[length + 1];

            // Copy the elements from the current row to the new array
            for (int i = 0; i < length; i++) {
                newRow[i] = groups[remainder][i];
            }

            // Add the number to the end of the new array
            newRow[length] = number;

            // Replace the current row with the new array
            groups[remainder] = newRow;
        }

        // Return the 2D array
        return groups;
    }

    // A main method to test the method
    public static void main(String[] args) {
        // Create an array of numbers
        int[] numbers = {1, 2, 3, 4, 5, 6, 7};

        // Call the method and print the result
        int[][] result = groupByRemainder(numbers);
        for (int i = 0; i < result.length; i++) {
            System.out.print(i + " -> ");
            for (int j = 0; j < result[i].length; j++) {
                System.out.print(result[i][j] + " ");
            }
            System.out.println();
        }
    }
}