docs: public static int[] Concatenate(int[] array, int[] array2) {
          int[] all = new int[array.length + array2.length];
          int idx = 0;
  
          //First array
          for (int i = 0; i < array.length; i++)
              all[idx++] = array[i];
  
          //Second array
          for (int i = 0; i < array2.length; i++)
              all[idx++] = array2[i];
  
          return all;
      }