java - 如何将二维数组中一行中的所有数字相加

Question

I am writing Java in Eclipse IDE, I have this 2D array:

public static void main(String[] args) {
int[][] fravaer18S = {
{ 2, 0, 0, 0, 3, 1, 0, 2, 0, 0, 0, 0 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 2, 0, 0, 0, 3, 1, 0, 2, 0, 0, 0, 0 },
{ 1, 2, 1, 2, 1, 2, 0, 2, 0, 0, 4, 0 },
{ 5, 0, 0, 0, 0, 0, 0, 9, 0, 0, 0, 0 }};

In another Class, I am supposed to write code so that a person can give a column number, and all numbers from that column is then added together.

So f.ex. a person gives row 3, and the code returns 15.

This stump of code was given:

 public int samletFravaer(int[][] fravaer, int elevNr) {
    // TODO
    return -1;

How do I code that? And what do I need to write in my main?

Answer 1

Add boundry conditions or exception handling on your own.

public int samletFravaer(int[][] fravaer, int elevNr) {
    int sum = 0;
    for (int i = 0; i < fravaer[elevNr].length; i++) {
      sum += fravaer[elevNr][i];
    }
    return sum;
  }

Answer 2

Could also be done using foreach loop

public static int samletFravaer(int[][] fravaer, int elevNr){
    int ri = 0;
    for(int i: fravaer[elevNr]){
        ri += i;
    }
    return ri;
}