用java定义两个二维数组，分别用于存储两个3*3的矩阵的元素值，求出这两个 矩阵的乘积，并输出计算结果。

在Java中，我们可以首先定义两个3x3的二维数组来存储矩阵的元素，然后创建一个方法来计算这两个矩阵的乘积。这里是一个简单的例子：

public class Main {
    static int[][] matrix1 = { {1, 2, 3}, {4, 5, 6}, {7, 8, 9} };
    static int[][] matrix2 = { {9, 8, 7}, {6, 5, 4}, {3, 2, 1} };

    // 计算两个矩阵相乘
    public static int[][] multiplyMatrices(int[][] first, int[][] second) {
        int rowsFirst = first.length;
        int colsFirst = first[0].length;
        int rowsSecond = second.length;
        int colsSecond = second[0].length;

        if (colsFirst != rowsSecond) {
            throw new IllegalArgumentException("Matrix dimensions don't allow multiplication");
        }

        int[][] result = new int[rowsFirst][colsSecond];
        for (int i = 0; i < rowsFirst; i++) {
            for (int j = 0; j < colsSecond; j++) {
                for (int k = 0; k < colsFirst; k++) {
                    result[i][j] += first[i][k] * second[k][j];
                }
            }
        }
        return result;
    }

    public static void main(String[] args) {
        int[][] product = multiplyMatrices(matrix1, matrix2);
        
        // 输出结果矩阵
        for (int[] row : product) {
            for (int element : row) {
                System.out.print(element + " ");
            }
            System.out.println();
        }