java - 链接列表中的对象

Question

我尝试编写一个代码，其中有一个带有一些选项的基本菜单。这些选项有以下方法:AddStudent、changeName、setGrade 等。我创建了一个名为 Student 的对象，它有姓名、年级和年龄。我想将学生添加到链接列表中，但是当我使用添加方法时它不起作用。这是我的代码:

import java.util.*;
class Student {  
    int age;
    int grade;
    String name;
    static LinkedList ll = new LinkedList();
    public Student (String n) {   //we create here a student with a name and an age
        name=n;
        age=0;
        grade=0;
    }
//-------------------------------------------------------------------------
    public void p(String x) {
        System.out.println(x);
    }

    public void addStudent() {
        Scanner s = new Scanner(System.in);
        p("Enter the name that you want");
        String f = s.nextLine();
        Student a = new Student(f);
        ll.add(a);
    }

    public void changeName() {                           //this method is to change the name of a student
        Scanner s = new Scanner(System.in);
        p("Enter whose name you want to change");  
        String c = s.nextLine();
        p("Enter the name that you want");
        String b = s.nextLine();

    }

    public void setGrade(Student a) {                 //this method is to put the student's grade
        Scanner s = new Scanner(System.in);
        p("Enter the grade that you want");
        int g = s.nextInt();
        a.grade=g;
    }

    public void setAge(Student a) {                 //This method is to put the student's grade
        Scanner s = new Scanner(System.in);
        p("Enter the age that you want");
        int h = s.nextInt();
        a.age=h;
    }

    public String getName(Student a) {
        return a.name;
    }

    public int getAge(Student a) {
        return a.age; 
    }

    public int getGrade(Student a) {
        return a.grade; 
    }
}

问题出在addStudent方法上。还有其他方法可以用来制作相同的项目吗？

Answer 1

从逻辑上思考这个问题。您有一个代表单个学生的 Student 类。为什么学生会有学生名单？这没有任何意义。

您是否没有一个类似Course 的程序或可以保存学生列表的程序？那就是你的列表所属的地方。除非有令人信服的理由(罕见)，否则不要使用静态。

这里是 Course 类的开始，它使用 Student 来存储学生信息，并将其存储在 LinkedList 中的 类(class)。您仍然需要实现 findStudent 方法，并且可能还需要实现打印列表的方法:

类(class):

import java.util.LinkedList;
import java.util.Scanner;

public class Course {
    LinkedList ll = new LinkedList();
    Scanner s = new Scanner(System.in);

    public void addStudent() {
        p("Enter the name that you want");
        String f = s.nextLine();
        Student a = new Student(f);
        ll.add(a);
    }

    public void changeName() {                           //this method is to change the name of a student
        Student student = findStudent();
        p("Enter the name that you want");
        String newName = s.nextLine();
        //student.setName(newName);
    }

    public void setGrade() {                 //this method is to put the student's grade
        Student student = findStudent();
        p("Enter the grade that you want");
        int grade = s.nextInt();
        //student.setGrade(grade);
    }

    public void setAge() {                 //This method is to put the student's grade
        Student student = findStudent();
        p("Enter the age that you want");
        int age = s.nextInt();
       student.setAge(age);
    }

    public Student findStudent(){
        p("Which student did you want to change? Please enter their name:");
        String name = s.nextLine();
        //Find student in the list - left for the author
        Student student = null;
        return student;
    }

    //-------------------------------------------------------------------------
    public void p(String x) {
        System.out.println(x);
    }

    public static void main(String[] args) {
        Course course = new Course();
        course.addStudent();
        course.addStudent();
        course.changeName();
        course.setGrade();
    }
}

修改后的Student类:

import java.util.*;

public class Student {
    int age;
    int grade;
    String name;

    public Student (String n) {   //we create here a student with a name and an age
        name=n;
        age=0;
        grade=0;
    }

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

    public void setGrade(int grade) {
        this.grade = grade;
    }

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

    public String getName(Student a) {
        return a.name;
    }

    public int getAge(Student a) {
        return a.age;
    }

    public int getGrade(Student a) {
        return a.grade;
    }

    @Override
    public String toString(){
        return "Student(name:" + name + ", age:" + age + ", grade:" + grade + ")";
    }
}