Java经典习题29

/*
题目：求一个3*3矩阵对角线元素之和。
*/

import java.util.*;

public class Class29 {

public static void main(String[] args) {
System.out.println("输入一个3*3矩阵");
Scanner sc = new Scanner(System.in);
int[][] a = new int[3][3];
System.out.println("请输入9个数字:");
for(int i = 0; i < 3; i++){
for(int j = 0; j < 3; j++){
a[i][j] = sc.nextInt();
}
}
System.out.println("显示这个矩阵:");
for(int i = 0; i < 3; i++){
for(int j = 0; j < 3; j++){
if(j < 3){
System.out.print(a[i][j]);
}
if(j == 2){
System.out.println();
}
}
}
System.out.println("现在开始计算:");
int sum = 0;
int sum1 = 0;
//主对角线
for(int i = 0; i < 3; i++){
for(int j = 0; j < 3; j++){
if(i == j){
sum1 += a[i][j];
}
}
}
int sum2 = 0;
//副对角线
for(int i = 0; i < 3; i++){
for(int j = 0; j < 3; j++){
if((i == 1)&&(j == 1)){
break;
}
if(i + j == 2){
sum2 += a[i][j];
}
}
}
sum = sum1 + sum2;
System.out.println("结果如下:");
System.out.println(sum);

}

}