29 求一个3*3矩阵对角线元素之和

题目:求一个3*3矩阵对角线元素之和

   public class _029MatrixSum {

    public static void main(String[] args) {
        matrixSum();
    }

    private static void matrixSum() {
        Scanner scanner = new Scanner(System.in);
        int[][] a = new int[3][3];
        System.out.println("请输入9个整数:");

        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                a[i][j] = scanner.nextInt();
            }
        }

        System.out.println("输入的3*3矩阵是:");
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                System.out.print(a[i][j] + " ");
            }
            System.out.println();
        }

        int sum = 0;
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                if (i == j) {
                    sum += a[i][j];
                }
            }
        }

        System.out.println("对角线之和是:" + sum);
    }
}