作为变量传递一个类 - 学校示例 - Java

Question

例如，我在绕过传递类作为变量时遇到了困难 - 例如 - 我正在考虑学校以及如何实现一个简单的系统来跟踪事物如

• 学生
• 教师
• 主题

使得下列条件：

• 一个学生需要主题
• 教师教一个主题
• 一个主题既有学生和教师

每个类的一个基本的例子是如如下：

Student.java

private String name; 
private int age; 
private Subject subject; 
private String school; // Can implement another class of School later 

public Student(int id, String name, int age, String school, String course) { 
    this.id = id; 
    this.name = name; 
    this.age = age; 
    this.school = school; 
    this.course = subject; 
} 

Teacher.java

private String name; 
private Subject subjectTaught; 
private Date taughtSince; // Date is another thing that perplexes me, but that can be saved for another time 
private int holidaysRemaining; 

public Teacher(int id, String name, Subject subjectTaught, String taughtSince, int holidaysRemaining) { 
    this.id = id; 
    this.name = name; 
    this.subjectTaught = subjectTaught; 
    this.taughtSince = taughtSince; 
    this.holidaysRemaining = holidaysRemaining; 
} 

主题

String name; 
int length; 
Teacher teacher; 
Student student; 

public Subject(int id, String name, int length, Teacher teacher, Student student) { 
    this.id = id; 
    this.name = name; 
    this.length = length; 
    this.teacher = teacher; 
    this.student = student; 
} 

我明白，我可以实现一个ArrayList或主题内的HashMap来跟踪哪些学生服用哪些科目等。

我只是有点失落，当涉及到实际得到的代码下来，使事情发生......

的最终结果将是有某种用于CRUD操作的库存管理系统“，增加学生和教师对象等

任何指导将是伟大的！

Answer 1

我认为Student.java和Teacher.java应该有Subject[] subjects而不是Subject subject。由于每个学生和老师都与许多主题相关，而不仅仅是一个。

Answer 2

在这种情况下，我不会推荐ArrayList，因为同一个对象可以在List中多次出现。您可以使用HashSet，在这种情况下，您需要在学生和教师课程中实施hashCode和equals。如果您实施Comparator<Student>和Comparator<Teacher>，则还可以使用TreeSet。假设一个对象是由它的ID字段标识，您也可以使用HashMap：

class Subject { 
    String name; 
    int length; 
    private final Map<Integer,Teacher> teachers = new HashMap<>(); 
    private final Map<Integer,Student> students = new HashMap<>(); 

    public Subject(int id, String name, int length) { 
     this.id = id; 
     this.name = name; 
     this.length = length; 
    } 

    public void addTeacher(Teacher teacher) { 
     teachers.put(teacher.getId(), teacher); 
    } 

    public void removeTeacher(Teacher teacher) { 
     teachers.remove(teacher.getId()); 
    } 

    public Teacher[] getTeachers() { 
     return teachers.values().toArray(new Teacher[teachers.size()]); 
    } 

    // ... same for students 
} 

Answer 3

也许这点你在正确的方向？ 我不确定我是否完全理解你的问题，请让我知道这是你正在寻找的！

public class School { 

    private String name; 
    private Map<String, Subject> subjects = new HashMap<>(); 

    public School(String name) { 
     this.name = name; 
    } 

    public String getName() { 
     return name; 
    } 

    public void addSubject(Subject subject) { 
     subjects.add(subject.name, subject); 
    } 

    public Subject getSubject(String name) { 
     return subjects.get(name); 
    } 
} 

public class Subject { 

    Map<String, Student> students = new HashMap<>(); 
    String name; 
    int length; 
    Teacher teacher; 

    public Subject(int id, String name, int length, Teacher teacher) { 
     this.id = id; 
     this.name = name; 
     this.length = length; 
     this.teacher = teacher; 
    } 

    public void addStudent(Student student) { 
     students.add(student.name, student); 
    } 

    public void getStudent(String name) { 
     students.get(name); 
    } 
}