class TwoDimArr {
    public static void main(String[] args) {
        int[][] arr = new int[3][];  //二维数组 动态初始化
        arr[0] = new int[3];
        arr[1] = new int[5];
        arr[2] = new int[2];

        arr[0][0] = 10;
        arr[1][0] = 50;

        int[][] arr1 = {{1, 2, 3}, {2, 4, 6, 8, 10}, {3, 5}};  //二维数组 静态初始化
        
        System.out.println(arr[0][0]);
        System.out.println(arr1[1][0]);
    }
}

输出结果：

10
2