import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class ScoreAverage {
    public static void main(String[] args) {
        String fileName = "scores.txt";
        int sum = 0;
        int count = 0;

        // try-with-resources 会自动关闭流，无需手动调用 close()
        try (BufferedReader br = new BufferedReader(new FileReader(fileName))) {
            String line;
            while ((line = br.readLine()) != null) {
                try {
                    int score = Integer.parseInt(line.trim());
                    sum += score;
                    count++;
                } catch (NumberFormatException e) {
                    System.err.println("数字格式错误，跳过无效数据行：" + line);
                }
            }

            if (count == 0) {
                System.out.println("文件中没有有效成绩数据，无法计算平均分。");
            } else {
                double average = (double) sum / count;
                System.out.printf("平均分：%.2f%n", average);
            }

        } catch (IOException e) {
            System.err.println("文件读取错误：" + e.getMessage());
        } catch (Exception e) {
            System.err.println("发生意外错误：" + e.getMessage());
        }
    }
}