关于IO流写入文件，一个你一定会遇到的问题 - 黑马程序员技术交流社区

package com.itheima;
import java.io.*;
import java.util.*;
/**
*
* 第2题：有五个学生，每个学生有3门课（语文、数学、英语）的成绩，写一个程序接收从键盘输入学生的信息，输入格式为：name,30,30,30（姓名，
* 三门课成绩），然后把输入的学生信息按总分从高到低的顺序写入到一个名称"stu.txt"文件中。要求：stu.txt文件的格式要比较直观，打开这个文件，
* 就可以很清楚的看到学生的信息。
*
*/
public class Test2 {
public static void main(String[] args) throws IOException {
//定义学生成绩
StudentScore ss = null;
//创建学生管理系统
StudentManage sm = new StudentManage();
//读取键盘录入
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
//定义一行数据
String line = null;
//按照提示进行选择功能
while (true) {
System.out.println("请按以下提示选择功能");
System.out.println("添加学生成绩请按1");
System.out.println("查找学生成绩请按2");
System.out.println("修改学生成绩请按3");
System.out.println("注销学生信息请按4");
System.out.println("排序输出所有学生信息请按5");
System.out.println("退出请按0");
//读取按下的数字
String number = br.readLine();
//根据数字选择功能
if (number.equals("1")) {
System.out.println("请输入姓名:");
String name = br.readLine();
System.out.println("请输入语文成绩:");
double chineseScore = Double.parseDouble(br.readLine());
System.out.println("请输入数学成绩:");
double mathScore = Double.parseDouble(br.readLine());
System.out.println("请输入英语成绩:");
double englishScore = Double.parseDouble(br.readLine());
ss = new StudentScore(name, chineseScore, mathScore,
englishScore);
sm.addScore(ss);
} else if (number.equals("2")) {
System.out.println("请输入你要查找的学生姓名:");
String name = br.readLine();
sm.lookUp(name);
} else if (number.equals("3")) {
System.out.println("请输入你要修改的学生姓名:");
String name = br.readLine();
System.out.println("请输入修改后的语文成绩:");
double chineseScore = Double.parseDouble(br.readLine());
System.out.println("请输入修改后的数学成绩:");
double mathScore = Double.parseDouble(br.readLine());
System.out.println("请输入修改后的英语成绩:");
double englishScore = Double.parseDouble(br.readLine());
sm.reviseScore(name, chineseScore, mathScore, englishScore);
} else if (number.equals("4")) {
System.out.println("请输入你要注销的学生姓名:");
String name = br.readLine();
sm.delete(name);
} else if (number.equals("5")) {
sm.scoreSort();
} else if (number.equals("0")) {
System.out.println("祝您生活愉快，再见");
System.exit(0);
} else {
System.out.println("输入有误");
}
}
}
}
/**
*
* 学生管理系统类成员变量：ArrayList 方法：添加，查询,修改，注销学生信息
*
*/
class StudentManage {
// 定义list，用来存储StudentScore对象
private List<StudentScore> list = null;
// 构造方法，初始化list
public StudentManage() {
list = new ArrayList<StudentScore>();
}
public List<StudentScore> getList() {
return list;
}
public void setList(List<StudentScore> list) {
this.list = list;
}
// 添加学生成绩
public void addScore(StudentScore score) {
list.add(score);
System.out.println("添加学生成绩成功");
}
// 查询学生成绩
public void lookUp(String name) {
int i;
for (i = 0; i < list.size(); i++) {
StudentScore student = (list.get(i));
if (name.equals(student.getName())) {
System.out.println("该学生信息为：");
System.out.println("姓名：" + name);
System.out.println("语文成绩： " + student.getChineseScore());
System.out.println("数学成绩： " + student.getMathScore());
System.out.println("英语成绩: " + student.getEnglishScore());
break;
}
}
if (i == list.size()) {
System.out.println("对不起，没有此学生信息");
}
}
// 修改学生成绩
public void reviseScore(String name, double chineseScore, double mathScore,
double englishScore) {
System.out.println(chineseScore);
int i = 0;
for (i = 0; i < list.size(); i++) {
StudentScore student = list.get(i);
System.out.println(chineseScore);
if (name.equals(student.getName())) {
System.out.println(chineseScore);
student.setChineseScore(chineseScore);
student.setMathScore(mathScore);
student.setEnglishScore(englishScore);
System.out.print(student.getChineseScore());
System.out.println("修改成绩成功 ");
break;
}
}
}
// 注销学生信息
public void delete(String name) {
int i = 0;
if (list.size() == 0) {
System.out.println("对不起，学生信息列表为空,请添加学生信息");
}
for (i = 0; i < list.size(); i++) {
StudentScore student = list.get(i);
if (name.equals(student.getName())) {
list.remove(i);
System.out.print("注销学生信息成功");
}
break;
}
if (i == list.size() && (list.size() != 0)) {
System.out.println("对不起，没有此学生信息");
}
}
// 按学生成绩总分从高到低进行排序
public void scoreSort() throws IOException {
FileWriter fw = null;
Collections.sort(list);
for (int i = list.size() - 1; i >= 0; i--) {
String s = list.get(i).getInfo();
fw = new FileWriter("src/stu.txt", true);
fw.write(s);
fw.write("\r\n");
fw.flush();
System.out.println(s);
}
}
}
/**
*
* 学生成绩类成员变量：语文，数学，英语成绩方法：get();set();
*/
class StudentScore implements Comparable<StudentScore> {
// 定义学生姓名
private String name;
// 定义语文，数学，英语成绩
private double chineseScore, mathScore, englishScore;
// 定义总成绩
private double sum;
// 带参数的构造方法，初始化语文，数学，英语成绩
public StudentScore(String name, double chineseScore, double mathScore,
double englishScore) {
this.name = name;
this.chineseScore = chineseScore;
this.mathScore = mathScore;
this.englishScore = englishScore;
this.sum = chineseScore + mathScore + englishScore;
}
// 自定义定义对象的比较规则
public int compareTo(StudentScore o) {
return Double.valueOf(this.sum).compareTo(Double.valueOf(o.sum));
}
// 定义获取学生成绩信息的方法
public String getInfo() {
return "姓名 :" + name + ";语文成绩: " + chineseScore + ";数学成绩: " + mathScore
+ ";英语成绩: " + englishScore + ";总成绩: " + sum;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getChineseScore() {
return chineseScore;
}
public void setChineseScore(double chineseScore) {
this.chineseScore = chineseScore;
}
public double getMathScore() {
return mathScore;
}
public void setMathScore(double mathScore) {
this.mathScore = mathScore;
}
public double getEnglishScore() {
return englishScore;
}
public void setEnglishScore(double englishScore) {
this.englishScore = englishScore;
}
}

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