程序代码：

public class Main {
  public static void main(String[] args) {
    int[] arr = { 1, 2, 3, 4, 5 ,6, 7, 8, 9 };
    for (int i = 0; i < arr.length; i++) {
      System.out.print(arr[i] + " ");
      if ((i + 1) % 3 == 0) {
        System.out.println();
      }
    }
  }
}