4.2 矩阵乘法，代码如下： //求两个方阵的乘积public static int[][] squareMatrixMultiply(int[][] a, int[][] b){int n = a.length;int[][] c = new int[n][n];for (int i = 0; i < n; i++){for (int j = 0; j < n; j++){c[i][j]