java - 在集合中添加元素

Question

我必须创建一个有一些本科生和研究生的类(class)，然后使用方法 getPostgraduates() 从类(class)中提取所有以“Ismael Bento”为导师的研究生，并使用类 Notifier 向他们发送消息(打印文本和收件人)。但是，没有打印任何内容...我的猜测是我的 getPostgraduates() 方法有问题。

这里是主要方法:

package students;

import java.util.*;

public class ProgrammingTest {

    public static void main (String[] args){
        Academic rr = new Academic("Ricardo Rodriguez");
        Academic ib = new Academic("Ismael Bento");
        Set<Student> students = new HashSet<Student>();

        Undergraduate ug1 = new Undergraduate("gg4", "Greg","gg4@", rr);
        Undergraduate ug2 = new Undergraduate("pr3", "Pete","pr3@", ib);
        Postgraduate pg1 = new Postgraduate("te2", "Ted", "te2@", rr);
        Postgraduate pg2 = new Postgraduate("yj34", "Yao", "yj34@", ib);
        Postgraduate pg3 = new Postgraduate("jj8", "Jack", "jj8@", ib);

        students.add(ug1);
        students.add(ug2);
        students.add(pg1);
        students.add(pg2);
        students.add(pg3);

        Course c1 = new Course("c1", students);
        Set<? extends Notifiable> n = c1.getPostgraduates("Ismael Bento");
        Notifier notifier = new Notifier(n);
        notifier.doNotifyAll("You have been notified!");

    }

}

和类(class)类(class):

package students;

import java.util.*;

public class Course {

    private Set<Student> students;
    private String name;

    public Course (String name, Set<Student> students){
        this.name = name;
        this.students = students;
    }

    public Set<Postgraduate> getPostgraduates(String nameOfSupervisor){
        Set<Postgraduate> postgraduates = new HashSet<Postgraduate>();

    for(Postgraduate p : postgraduates) {  
        if (p.getSupervisor().equals(nameOfSupervisor)){
            postgraduates.add(p);
        }
    }
        return postgraduates;

    }

}

和通知类:

package students;
import java.util.Iterator;
import java.util.Set;

public class Notifier {
    Set<? extends Notifiable> notifiables;

    public Notifier (Set<? extends Notifiable> n) {
        notifiables = n;
    }

    public void doNotifyAll(String message) {

        Iterator<? extends Notifiable> i = notifiables.iterator();
        while(i.hasNext()){
            i.next().notify();
        }


    }
}

Answer 1

问题确实出在getPostgraduates()中。这样做的原因是，您只能与用空值初始化的对象 postgraduate 进行比较。你应该把整个学生群都跑一遍，研究生找你要找的导师去查。