java - 如何返回一个子类独有的变量？

Question

我有一个类Person，它有多个子类。所有子类都有相同的变量(name、address、phone)，但有一个额外的变量，rank 。我知道如何显示姓名、地址、电话，但我不知道如何显示排名。

定义类:

public class Person {
    public String name;
    public String address;
    public String phone;

    public Person(String name, String address, String phone) {
        this.name = name;
        this.address = address;
        this.phone = phone;
    }

    public String toString() {
        return this.getClass().getName() + "\n" + name;
    }
}

使用rank定义子类:

public class Pupil extends Person {
    public String rank;
    public Student(String name, String address, String phone, String rank) {
        super(name, social, phone);
    }

}

创建学生并显示姓名、地址和电话。

public class Test {

public static void main(String[] args) {
Person person = new Person("John", "1 John Deer Rd", "1112223333");
Person pupil = new Pupil("Jane", "2 John Deer Rd", "1112223333", "junior");


System.out.println(pupil.name + "'s phone is " + pupil.phone + " and their address is " + pupil.address + "." + "\n");

}
}

如何显示排名？

Answer 1

您必须将对象从 Person 转换回 Pupil:

((瞳孔)瞳孔).rank

如果您不能 100% 确定您的对象实际上是学生，您应该添加健全性检查:

if(pupil instanceof Pupil) {
    System.out.println(…+((Pupil)pupil).rank+…);
}