Task 2. Create a list of students by reading from student_hobbies.txt and display the list. // - You will also need to create a Student class, which has at least // two data fields: student name and an ArrayList of hobbies (String-type).优化以下代码private static ArrayList<Student> readFile(String string) throws IOException{ ArrayList<Student> studentlist=new ArrayList<Student>(); File file = new File("student_hobbies_JU.txt"); Scanner scanner = new Scanner(file); while (scanner.hasNextLine()) { String line = scanner.nextLine(); String[] data = line.split(", "); System.out.println(data); String name = data[0]; ArrayList<String> hobbies = new ArrayList<String>(); for(int i=0;i<data.length;i++){ hobbies.add(data[i]); } Student student = new Student(name, hobbies); studentlist.add(student); System.out.println(student); } scanner.close(); return studentlist; }//end readFile

下面是优化后的代码，其中将文件名作为参数传入函数中，使函数更加通用：

private static ArrayList<Student> readFile(String fileName) throws IOException {
    ArrayList<Student> studentList = new ArrayList<Student>();
    File file = new File(fileName);
    Scanner scanner = new Scanner(file);
    while (scanner.hasNextLine()) {
        String line = scanner.nextLine();
        String[] data = line.split(", ");
        String name = data[0];
        ArrayList<String> hobbies = new ArrayList<String>();
        for (int i = 1; i < data.length; i++) { // 从第二个元素开始，将所有的兴趣爱好添加到hobbies列表中
            hobbies.add(data[i]);
        }
        Student student = new Student(name, hobbies);
        studentList.add(student);
    }
    scanner.close();
    return studentList;
}

该函数将指定文件中的内容读取到一个ArrayList<Student>中，并返回该列表。下面是Student类的代码：

public class Student {
    private String name;
    private ArrayList<String> hobbies;

    public Student(String name, ArrayList<String> hobbies) {
        this.name = name;
        this.hobbies = hobbies;
    }

    public String getName() {
        return name;
    }

    public ArrayList<String> getHobbies() {
        return hobbies;
    }

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

    public void setHobbies(ArrayList<String> hobbies) {
        this.hobbies = hobbies;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", hobbies=" + hobbies +
                '}';
    }
}

该类包含两个数据字段：name和hobbies，分别表示学生的姓名和兴趣爱好列表。该类还包含构造函数、getter和setter方法以及toString方法，用于打印学生对象的信息。可以使用以下代码调用readFile函数并打印学生列表：

try {
    ArrayList<Student> studentList = readFile("student_hobbies.txt");
    for (Student student : studentList) {
        System.out.println(student);
    }
} catch (IOException e) {
    e.printStackTrace();
}