flatten 2d array

// package whatever; // don't place package name!

import java.io.*;
import java.util.*;
/**
 * 2e. Flatten a two dimensional integer array
 *
 * Input:   two-dimensional Integer Array
 * Output:  Array of Integers
 *
 * Example: int matrix[][]= {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
 *          Flatten.compute(matrix) =>
 *          {1, 2, 3, 4, 5, 6, 7, 8, 9}
 */
class Flatten {

    public static void main (String[] args) {
     int[][] matrix ={{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
     System.out.println(Arrays.toString(compute(matrix)));
      }
    public static int[] compute(int[][] matrix) {
      int index = 0;
      int resultArr[] = new int[matrix.length * matrix[0].length];
      for(int i = 0; i< matrix.length; i++){
        for(int j =0 ; j< matrix[0].length; j++){
            resultArr[index++] = matrix[i][j];
        }
      }
    return resultArr;
    }

}