java - 类 创建方法时的返回类型

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[UML图][1]

我正在准备下周的期中考试，我正在练习教授给出的一些例子；但是，我在类返回类型方法方面遇到了一些麻烦。

为了以防万一，我附上了 UML 图。

我想要理解的是 Job 类中的 getPerson 方法。我认为我不需要 Job 类中的数组列表来存储所有员工。因为我已经在 Company 类中有一个数组列表。另外，返回类型是 Employee 类，我不确定如何使用此类返回类型获取人员信息。

我的问题

1. Job 类中的 public Employee getPerson() {}
2. Job 类中的 public boolean isVacant() {}
3. 另外，您介意检查一下 getVacantJobs、getFilledJobs 和 getAllJobs 方法是否正确构建吗？

我使用迭代器来显示所有存储的作业。

----------------------------------------员工类-------------------- -----------

public class Employee {
    private String name;
    private int id;

    public Employee(int id, String name) {
        this.name = name;
        this.id =id;

    }

    public final String getName() {
        return name;
    }

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

    public final int getId() {
        return id;
    }

    public final void setId(int id) {
        this.id = id;
    }

    @Override
    public String toString() {
        return "Employee [name=" + name + ", id=" + id + "]";
    }

}

----------------------------------------职位类别----------------- ----------------------------------

public class Job {

    private String description;

    private int id;
    private double maxSalary;

    public Job(int id, double maxSalary, String description) {
        this.description = description;
        this.id = id;
        this.maxSalary = maxSalary;
    }

    public Job(int id, double maxSalary, String description, Employee e1) {
        this.description = description;
        this.id = id;
        this.maxSalary = maxSalary;



    }

    @Override
    public String toString() {

        return "Job [description=" + description + ", id=" + id
                + ", maxSalary=" + maxSalary + "]";
    }

    public final String getDescription() {
        return description;
    }

    public final void setDescription(String description) {
        this.description = description;
    }

    public final double getMaxSalary() {
        return maxSalary;
    }

    public final void setMaxSalary(double maxSalary) {
        this.maxSalary = maxSalary;
    }

    public final int getId() {
        return id;
    }

    public Employee getPerson() {
        retrun 
    }

    public final void setPerson(Employee person) {
        this.id = person.getId();

    }
}

--------------------------公司类-------------------- --------

import java.util.ArrayList;
import java.util.Iterator;

public class Company {

    static ArrayList list = new ArrayList();
    Iterator itr = list.iterator();


    private String name;

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

    public Company() {
        // TODO Auto-generated constructor stub
    }

    public static void addJob(Job j1) {
        list.add(j1);
    }

    public void removeJob(int id) {
        list.remove(id);

    }


    public ArrayList<Job> getVacantJobs() {
        while (itr.hasNext()) {
            if ((itr == null)) {
                System.out.println(itr);
            }
        }
        return null;

    }

    public ArrayList<Job> getFilledJobs() {
        while (itr.hasNext()) {
            if (!(itr == null)) {
                System.out.println(itr);
            }
        }
        return null;
    }

    public ArrayList<Job> getAllJobs() {
        while (itr.hasNext()) {
            System.out.println(itr.next());
        }
        return null;
    }

}

Answer 1

将字段person添加到Job类。

public class Job {

    // .....

    private Employee person;

    public Employee getPerson() {
        return person;
    }

    public final void setPerson(Employee person) {
        this.person = person;
    }

    public boolean isVacant() {
        return person == null;
    }
}

并将 jobs 字段添加到 Company 类中。

public class Company {

    // static ArrayList list = new ArrayList();  // You don't need this
    // Iterator itr = list.iterator();  // You don't need this.

    // .....

    private ArrayList<Job> jobs = new ArrayList<>();

    public ArrayList<Job> getVacantJobs() {
        ArrayList<Job> result = new ArrayList<>();
        for (Job job : jobs)
            if (job.isVacant())
                result.add(job);
        return result;
    }

    public ArrayList<Job> getFilledJobs() {
        ArrayList<Job> result = new ArrayList<>();
        for (Job job : jobs)
            if (!job.isVacant())
                result.add(job);
        return result;
    }

    public ArrayList<Job> getAllJobs() {
        ArrayList<Job> result = new ArrayList<>();
        for (Job job : jobs)
            result.add(job);
        return result;
    }
}