使用字符流编程实现以下功能

*从键盘输入姓名、学号、成绩，并保存到文本文件中，重复进 行，直到输入空字符串为止

*从文件中读取各学生的成绩，并计算所有学生成绩的平均值、最大值、最小值和总分。

这个程序还有很多可以改进，比如如何确定成绩，当有的成绩大于100时，有的为个位数时又该如何subString,事实上这种截取成绩的方法太拙劣，不合适。 -Character stream programming the following features

From the keyboard and enter your name, student number, results, and save to a text file, repeated until you enter an empty string

* Read from the file of each student s achievements, and calculate the average of all student performance, maximum, minimum, and the total score.

This program can be improved, such as how to determine the results, some results greater than 100, some digits Shiyou how

subString, in fact this interception of the results is too clumsy, inappropriate