Parsing 从文件中提取一个值

我试图做的是从文件中获取变量，但如果输入不是数字，则抛出异常。我只想在输入的金额是一个字或负数时显示一条错误消息。我想用试一试，但不知道如何组织它。谢谢你们

 StreamReader read = new StreamReader("../../data.dat");
        Stopwatch st = new Stopwatch();
        bool ok;
        int num;
        string input=(read.ReadLine());
        ok = int.TryParse(input, out num);
        if (ok ==false)
        {
            throw new Exception("Input in incorrect format");
        }
        int sum = 0;

Scanner scan = new Scanner("../../data.dat");
int num = Integer.MIN_VALUE;
try {
    num = Integer.parseInt(scan.next());
} catch (Exception e) {
    System.out.println("Input in incorrect format.");
    e.printStackTrace();
}
scan.close();