矩陣

import java.util.Scanner;  
  
public class sum {  
  
    public static void main(String[] args) {  
        /** 
         * 求一個n階方陣對角線元素之和。 
         */  
        int N,sum=0;  
        // TODO Auto-generated method stub  
        /*Scanner sc=new Scanner(System.in); 
        N=sc.nextInt();*/  
        int a[][]=new int[][]{{1,2,3,4},{1,2,3,4},{1,2,3,4},{1,2,3,4}} ;  
        sum=sum(a,4);  
        System.out.println("對角線元素之和為"+sum);  
    }  
     static int sum(int a[][],int N)  
    {  
        int i,j,sum=0;  
        for( i=0;i<N;i++ )  
                sum += a[i][i];  
        return  sum ;  
  
    }  
}