java/w7/1

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

public class ScoreAverage {
    public static void main() {
        double sum = 0;
        int count = 0;
        double scoreAverage = 0;

        try(BufferedReader br = new BufferedReader(new FileReader("scores.txt"))) {
            String line;
            while ((line = br.readLine()) != null) {
                sum += Integer.parseInt(line);
                count += 1;
            }

            if (count == 0){
                System.out.println("文件中无有效数据");
            }else{
                scoreAverage = sum / count;
                System.out.printf("由该文件中数据可得平均分为%.2f",scoreAverage);
            }
        } catch (FileNotFoundException e) {
            System.out.println("文件不存在");
            e.printStackTrace();
        } catch (NumberFormatException e) {
            System.out.println("数字格式错误");
            e.printStackTrace();
        } catch (IOException e) {
            System.out.println("文件读取发生错误");
            e.printStackTrace();
        }
    }
}