Question

我应该让教授成为一门课程的导师。方法上方的评论也说明了目标。但是我很困惑如何解决这个问题。我是java编程的新手，所以我决定通过“instanceof”比较检查教授是否在课程中。我是朝着正确的方向前进还是我错过了什么？谢谢！

接近结束时，我添加了其他两个我刚遇到的方法，我相信我错误地实现了我的getStudents。最后两种方法要求添加学生并删除。我不确定学生的键值对是什么。

public class Course实现了Comparable {

/**
 * course id (unique)
 */
private int id;
/**
 * course name
 */
private String name;
/**
 * course level
 */
private int level;
/**
 * professor teaching the course, null if none
 */
private String professor;
/**
 * students enrolled in the course (unique), empty if none
 */
private HashSet<String> students;

/**
 * Create a course. Initially there is no professor or student for the
 * course.
 *
 * @param id course id
 * @param name course name
 * @param level course level
 */
public Course(int id, String name, int level) {
    this.id = id;
    this.name = name;
    this.level = level;
    this.professor = null;
    this.students = new HashSet<>();
}

/**
 * Get the course id.
 *
 * @return course id
 */
public int getId() {
    return id;
}

/**
 * Get the course name.
 *
 * @return course name
 */
public String getName() {
    return name;
}

/**
 * Get the course level.
 *
 * @return course level
 */
public int getLevel() {
    return level;
}

/**
 * Get the professor teaching the course.
 *
 * @return the professor, if none, null
 */
public String getProfessor() {
    return professor;
}

/**
 * Get the students enrolled in the course.
 *
 * @return the students, organized by ascending hash codes. if there are no
 * students enrolled the list should be empty.
 */
public Collection<String> getStudents() {
    return students;
}

/**
 * Make a professor the instructor of this course. If another professor was
 * teaching it, that information is lost.
 *
 * @param username the username of the professor
 */
public void addProfessor(String username) {

}

} / **

如果学生未注册，请将其添加到课程中
恒定时间。 *
@param username学生的用户名
@return是否添加了学生 * / public boolean addStudent（String username）{ //去做返回false; }

/ **

从课程中删除学生，如果他们已注册，
恒定时间。 *
@param username要移除的学生的用户名
@return如果学生被移除则为true，如果学生不在课程中，则为false * / public boolean removeStudent（String username）{ // 去做返回false; }

Answer 1

您可以在professor上调用getter来检查它是否已设置。

public void addProfessor(String professor) {
     if(this.getProfessor() == null || this.getProfessor().isEmpty()) {
         this.setProfessor(professor);
     }
}

Answer 2

只需实现方法addProfessor -

public void addProfessor(String username) {
    /*
    This assignment will replace any other professor
    who are teaching of this course.
    If you assign the class variable **professor**,
    when you call getProfessor(), that will return
    username this professor.
    */
    this.professor = username;
}

Answer 3

使用instanceof关键字检查对象在运行时是否属于特定类型。在这种情况下，评论指出如果先前设置了一个值，那么它就会丢失。这意味着你可以简单地将给定值设置为教授而不进行任何检查

public void addProfessor(String userName) {
    professor = userName;
}

添加和删除元素

3 个答案:

添加和删​​除元素

3 个答案:

添加和删除元素