有9行18列二维数组，请用java将列(4,10)(2,12)(0,15)(6,16)(3,14)(9,13)(8,17)(1,7)(5,11)计算均值合并为9行9列的二维数组。 再将所有9行9列二维数组中(i,j)和(j,i)两个元素合并计算均值，形成三角形矩阵数组。

下面是Java代码实现：

public class Main {
    public static void main(String[] args) {
        int[][] originalArray = new int[][]{{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18},
                {19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36},
                {37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54},
                {55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72},
                {73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90},
                {91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108},
                {109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126},
                {127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144},
                {145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162}};

        int[][] mergedArray = new int[9][9];

        for (int i = 0; i < mergedArray.length; i++) {
            for (int j = 0; j < mergedArray[i].length; j++) {
                int sum = 0;
                int count = 0;
                if (i < j) {
                    sum += originalArray[i][4] + originalArray[j][4];
                    count += 2;
                }
                if (i < j - 1 || i > j + 1) {
                    sum += originalArray[i][10] + originalArray[j][10];
                    count += 2;
                }
                if (i < j - 2 || i > j + 2) {
                    sum += originalArray[i][15] + originalArray[j][15];
                    count += 2;
                }
                if (i < j - 3 || i > j + 3) {
                    sum += originalArray[i][16] + originalArray[j][16];
                    count += 2;
                }
                if (i < j - 1) {
                    sum += originalArray[i][14] + originalArray[j][14];
                    count += 2;
                }
                if (i < j + 1) {
                    sum += originalArray[i][13] + originalArray[j][13];
                    count += 2;
                }
                if (i < j) {
                    sum += originalArray[i][17] + originalArray[j][17];
                    count += 2;
                }
                if (i > j) {
                    sum += originalArray[i][7] + originalArray[j][7];
                    count += 2;
                }
                if (i > j + 1 || i < j - 1) {
                    sum += originalArray[i][11] + originalArray[j][11];
                    count += 2;
                }
                mergedArray[i][j] = count == 0 ? 0 : sum / count;
                mergedArray[j][i] = mergedArray[i][j];
            }
        }

        int[][] triangleArray = new int[9][9];

        for (int i = 0; i < triangleArray.length; i++) {
            for (int j = 0; j <= i; j++) {
                int sum = mergedArray[i][j] + mergedArray[j][i];
                triangleArray[i][j] = triangleArray[j][i] = sum / 2;
            }
        }

        for (int i = 0; i < triangleArray.length; i++) {
            for (int j = 0; j < triangleArray[i].length; j++) {
                System.out.print(triangleArray[i][j] + " ");
            }
            System.out.println();
        }
    }
}