二维数组

        int[][] acc = new int[2][4];
        System.out.println(acc.length);  //2
        System.out.println(acc[1].length); //4

        int[][] acc = new int[][]{{1, 2, 3}, {3, 2, 1}};
        for (int i = 0; i < acc.length; i++) {
            for (int j = 0; j < acc[i].length; j++) {
                System.out.print(acc[i][j] + ",");
            }
            System.out.println();
        }