Student.java

import java.util.HashSet;  
import java.util.Set;  

public class Student{  
    public String id;   
    public String name;  
    public String age;  
    public Set<Course> course;  
    public Student(String id,String name) {  
        this.id=id;  
        this.name=name;  
        course=new
 
 HashSet<Course>();  
    }  
    public String getAge() {  
        return age;  
    }  
    public void setAge(String age) {  
        this.age = age;  
    }  
    public void ForEach() {  
        System.out.println("已選課程：");  
        for(Object obj:course) {  
            Course cr=(Course) obj;  
            System.out
 
.println("課程  "+cr.id+"："+cr.name);  
        }  
    }  
}  

Course.java

public class Course {  
    public String id;  
    public String name;  
    public Course(String id,String name) {  
        this.id=id;  
        this.name=name;  
    }  
}

StudentList.java

import java.util.HashMap;  
import java.util.Map;  
import java.util.Scanner;  

public
 
 class StudentList {  
    public Map <String, Student> students=new HashMap <String ,Student>() ;  
    Scanner input=new Scanner(System.in);  
    public void addStudent(int n) {  
        while(n>0) {  
            System.out.println("請輸入學生ID");  
            String id=input.nextLine();  
            Student st=students.get(id);  
            if(st==null) {  
                System.out.println("請輸入學生姓名");  
                String name=input.nextLine();  
                Student stu1=new Student(id,name);   
                students.put(id, stu1);  
                System.out.println("成功新增學生："+stu1.name);      
            }else {  
                System.out.println("該學生已存在");     
            }  
            n--;  
        }  
    }  
    public void ShowStudent(){  
        System.out.println("已存在學生：");  
        for(String key:students.keySet()) {  
            Student temp=students.get(key);   
            System.out.println(temp.id+": "+temp.name);  
        }  
    }         
}  

CourseList.java

import java.util.ArrayList;  
import java.util.List;  
import java.util.Scanner;  

public class CourseList {  
        public List<Course> courses;  
        public CourseList() {  
            courses=new ArrayList<Course>();  
        }  
        public void AddCourse(int n) {  
            for(int i=1;i<=n;i++) {  
                @SuppressWarnings("resource")  
                Scanner input=new Scanner(System.in);  
                System.out.println("請輸入課程ID");  
                String id=input.nextLine();  
                System.out.println("請輸入課程名字");  
                String name=input.nextLine();  
                Course add=new Course(id,name);  
                courses.add(add);  
                System.out.println("成功新增課程："+name);  
            }  
        }  
        public void ShowCourse(){  
            int size=courses.size();   
            System.out.println("已存在課程：");  
            for(int i=0;i<size;i++) {  
                Course temp=(Course)courses.get(i);  
                System.out.println(temp.id+": "+temp.name);  
            }  
        }         
}

StuTest.java

import java.util.Scanner;  

public class StuTest {  
    CourseList C=new CourseList();  
    StudentList S=new StudentList();  
    static Scanner input=new Scanner(System.in);  
    public void addCourse() {  
        System.out.println("請輸入需要新增課程的數量");  
        int n=input.nextInt();  
        C.AddCourse(n);  
        C.ShowCourse();  
    }  
    public void addStudent() {  
        System.out.println("請輸入需要新增學生的數量");  
        int n=input.nextInt();  
        S.addStudent(n);  
        S.ShowStudent();  
    }  
    public void ChooseCourse() {  
        System.out.println("請輸入學生ID");  
        String id=input.next();  
        Student st=(Student)S.students.get(id);  
        if(st==null){  
            System.out.println("此學生不存在");  
        }else {  
            C.ShowCourse();  
            System.out.println("請輸入課程ID");  
            int ID=input.nextInt();  
            Course add=(Course)C.courses.get(ID-1);  
            st.course.add(add);  
            System.out.println("成功新增課程"+add.id+"："+add.name);     
            }  
        }  
    public void Menu() {  
        System.out.println("===================================");  
        System.out.println("||          1.錄入學生資訊                 ||");  
        System.out.println("||          2.錄入課程資訊                 ||");  
        System.out.println("||          3.學生選課系統                 ||");  
        System.out.println("||          0.退出                              ||");  
        System.out.println("===================================");  
    }  
    public static void main(String[] args) {  
        StuTest P=new StuTest();              
        while(1<2) {  
        P.Menu();     
        int n=input.nextInt();  
        if(n==0) {break;}  
        switch (n) {  
        case 1:P.addStudent();break;  
        case 2:P.addCourse();break;  
        case 3:P.ChooseCourse();break;  
        case 0:n=0;break;  
        default: break;  
        }  
        }  
    }  
}