创建文件、修改数据

1. 复制上例中的Student类到本项目中；
2. 在项目目录下创建文件name.txt，并写入以下内容：
   it001,武松,男,22
   it002,林冲,男,20
   it003,卢俊义,男,18
   it004,石宝,男,23
3. 创建MainApp类，包含main()方法
4. 在main()方法中：
5. 定义一个存储Student对象的集合；
6. 循环从文件中读取数据，每次读取一行，并解析每个属性值，封装到一个Student对象中，并将这个对象封装到集合中。
7. 遍历集合，找到要修改的“卢俊义”，并将姓名修改为：“史文恭”。
   同时将数据再次写回到文件中。

8. 程序结束后，验证文件中的数据是否修改成功。 ```java package Day10.Demo03;/*

   @create 2020—11—26—18:26 */

public class Student { private String id; private String name; private String sex; private String age;

public Student() {
}
public Student(String id, String name, String sex, String age) {
    this.id = id;
    this.name = name;
    this.sex = sex;
    this.age = age;
}
public String getId() {
    return id;
}
public void setId(String id) {
    this.id = id;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public String getSex() {
    return sex;
}
public void setSex(String sex) {
    this.sex = sex;
}
public String getAge() {
    return age;
}
public void setAge(String age) {
    this.age = age;
}
@Override
public String toString() {
    return "Student{" +
            "id='" + id + '\'' +
            ", name='" + name + '\'' +
            ", sex='" + sex + '\'' +
            ", age='" + age + '\'' +
            '}';
}

}

```java
package Day10.Demo03;/*
    @create 2020--11--26--19:05
*/
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.util.ArrayList;
import java.util.Arrays;
public class MainApp {
    public static void main(String[] args) throws Exception{
        BufferedWriter f = new BufferedWriter(new FileWriter("name.txt"));
        f.write("it001,武松,男,22\n");
        f.write("it002,林冲,男,20\n");
        f.write("it003,卢俊义,男,18\n");
        f.write("it004,石宝,男,23\n");
        f.close();
        BufferedReader br = new BufferedReader(new FileReader("name.txt"));
        ArrayList<String> arr = new ArrayList<>();
        char[] chs = new char[14];
        int len;
        while ((len = br.read(chs)) != -1) {
            arr.add(new String(chs));
            System.out.println(new String(chs,0,len));
        }
        System.out.println(arr.get(0));
        ArrayList<Student> students = new ArrayList<>();
        for (int i = 0; i < arr.size()-1; i++) {
            String[] s = String.valueOf(arr.get(i)).replace("\n","").split(",");
            System.out.println(Arrays.toString(s));
            students.add(new Student(s[0], s[1], s[2], s[3]));
        }
        for (Student student : students) {
            if ("卢俊义".equals(student.getName())) {
                student.setName("史文恭");
            }
        }
        for (Student student : students) {
            System.out.println(student);
        }
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("name.txt"));
        for (Student student : students) {
            String s = student.getId()+","+student.getName()+","+student.getSex()+","+student.getAge()+"\n";
            bufferedWriter.write(s);
        }
        bufferedWriter.close();
        br.close();
    }
}