Java重写《C经典100题》 --38

 1 import java.util.Arrays;
 2 import java.util.Random;
 3 
 4 /**
 5  *
 6  *【程序38】 
 7  * 题目：求一个3*3矩阵对角线元素之和。
 8  * 程序分析：利用双重for循环控制输入二维数组，再将arr[i][i]累加后输出。
 9  * 
10  * @author www.cnblogs.com/java-100
11  *
12  */
13 
14 public class Java38 {
15 
16     public static void main(String[] args) {
17         int[][] arr = new int[3][3];
18         int sum = 0;
19         Random random = new Random();
20         for (int i = 0; i < arr.length; i++) {
21             for (int j = 0; j < arr[i].length; j++) {
22                 arr[i][j] = random.nextInt(100);
23                 System.out.print(arr[i][j] + " ");
24                 if (i == 0 && (j == 0 || j == 2) || i == 1 && j == i || i == 2 && (j == 0 || j == 2)) {
25                     sum += arr[i][j];
26                 }
27             }
28             System.out.println();
29         }
30         System.out.println(sum);
31     }
32 
33 }