java - 设置和显示名称和电子邮件 Java 对象类

Question

我有一个java类作业，它输入船员并显示他们的信息，我做过其他类似的案例，但不知道如何构建这个。我要创建两个类，Sailor 和 CrewMember，它们与这个 main 方法一起使用 -

import java.util.ArrayList;

public class SailorProgram {

    public static void main(String[] args) {

        Sailor firstSailor = new Sailor("Jimmy", "jimmy@mail.com");
        Sailor secondSailor = new Sailor("Rose", "rose@mail.com");
        Sailor thirdSailor = new Sailor("James", "james@sailors.com");


        CrewMember firstCrew = new CrewMember();
        CrewMember secondCrew = new CrewMember();

        firstCrew.addCrewMember(firstSailor);
        firstCrew.addCrewMember(secondSailor);

        secondCrew.addCrewMember(thirdSailor);
        secondCrew.addCrewMember(secondSailor);

        System.out.println(" First crew \n" + firstCrew);
        System.out.println(" Second crew \n" + secondCrew);

        secondSailor.setEmail("Rose@sailors.com");
        System.out.println(" Second crew \n" + secondCrew);
    }
}

然后打印出来

First crew
Jimmy (jimmy@mail.com)
Rose (rose@mail.com)

Second crew
James (james@sailors.com)
Rose (rose@mail.com)

Second crew
James (james@sailors.com)
Rose (rose@sailors.com)

谢谢!

Answer 1

addCrewMember() 是我们想知道的关键方法。如果将 Sailor 引用给 secondCrew 类，输出将会改变。

public class Sailor {
private String name;
private String email;

public Sailor(String name, String email) {
    this.name = name;
    this.email = email;
}

@Override
public String toString() {return name + " " + "(" + email + ")";}
}

如果 CrewMember.class 像下面这样

import java.util.ArrayList;

public class CrewMember {

private final ArrayList<Sailor> sailors = new ArrayList<>();

public void addCrewMember(Sailor s) { //add sailors with this
    sailors.add(s);
}
@Override
public String toString() { return sailors.toString(); }
}

并在问题中运行主要方法thr 输出是这样的:

 First crew 
 [Jimmy (jimmy@mail.com), Rose (rose@mail.com)]

 Second crew 
 [James (james@sailors.com), Rose (rose@mail.com)]

 Second crew 
 [James (james@sailors.com), Rose (Rose@sailors.com)]

Rose@sailors.com 发生了变化!因为 ArrayList sailors 保存了 Rose Sailor 的引用