代码实现目标：

将集合中的数据写道文件中通过字符缓冲输出流实现

代码展示

 public static void main(String[] args) throws IOException {
        //创建ArrayList集合
        ArrayList<Student> array = new ArrayList<>();

        //创建学生对象
        Student s1 = new Student("01", "朱文静", "30", "武汉");
        Student s2 = new Student("02", "zz", "22", "浙江");
        Student s3 = new Student("03", "ss", "33", "云南");

        //把学生对象添加到集合中
        array.add(s1);
        array.add(s2);
        array.add(s3);

        //创建字符缓冲输出流
        BufferedWriter bw = new BufferedWriter(new FileWriter("student.txt"));

        //遍历集合，得到每个学生对象
        for (Student s :array){
            //把学生对象的数据拼成指定格式的字符串
            StringBuilder sb = new StringBuilder();
            sb.append(s.getSid()).append(s.getName()).append(s.getAge()).append(s.getAddress());

            //调用字符缓冲输出流对象的方法写数据
            bw.write(sb.toString());
            bw.newLine();
            bw.flush();
        }
        //释放资源
        bw.close();
    }

public class Student {
    private String sid;
    private String name;
    private String age;
    private String address;

    public Student(String sid, String name, String age, String address) {
        this.sid = sid;
        this.name = name;
        this.age = age;
        this.address = address;
    }

    public String getSid() {
        return sid;
    }

    public void setSid(String sid) {
        this.sid = sid;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

运行结果