求二维数组a中的上三角元素之和。答:public class ArrayTest { public static void main(String[] args) { int arr[][]={{1,2,3},{4,5,6},{7,8,9}},tem=0,sum=0;for (int i = 0; i < arr.length; i++) { for (int j = 0; j < arr[i].length; j++) { System.out.print(arr[i][j]+" ");if(...