第一天：求二维数组中每个一维数组的元素之和

class three {public static void main(String[] args) {int[][] arr={{24,5,4,3},{5,43,4,5},{45,3,4,3}};int sum=0;for (int x=0;x<arr.length ;x++ ){for (int y=0;y<arr[x].length ;y++ ){sum=sum+arr[x][y];}}System.out.println("sum="+sum);}}