用鸿蒙系统定义一个接口person具有name、age、id_num属性以及方法print。创建两个类（学生、老师）分别实现上述接口

在HarmonyOS（鸿蒙系统）环境中，你可以使用其组件化和契约（Contract）的设计理念来定义接口和类。首先，我们定义一个名为`Person`的接口，包含属性和方法：

// person.contract
interface PersonContract {
    string getName();
    int getAge();
    string getIdNum();

    void print();
}

接下来，我们创建两个实现这个接口的类，分别是`Student`和`Teacher`：

// student.component
import "person.contract";
@Component
class Student: PersonContract {
    var name: string;
    var age: int;
    var idNum: string;

    constructor(name: string, age: int, idNum: string) {
        this.name = name;
        this.age = age;
        this.idNum = idNum;
    }

    override fun getName(): string {
        return name;
    }

    override fun getAge(): int {
        return age;
    }

    override fun getIdNum(): string {
        return idNum;
    }

    override fun print() {
        println("Student: Name - $name, Age - $age, ID - $idNum");
    }
}

// teacher.component
import "person.contract";
@Component
class Teacher: PersonContract {
    var name: string;
    var age: int;
    var subject: string;
    
    constructor(name: string, age: int, subject: string) {
        this.name = name;
        this.age = age;
        this.subject = subject;
    }

    override fun getName(): string {
        return name;
    }

    override fun getAge(): int {
        return age;
    }

    override fun getIdNum(): string {
        // 假设教师没有单独的ID，可以返回其他信息或者抛异常
        throw UnsupportedOperationException("Teachers do not have an ID_num.");
    }

    override fun print() {
        println("Teacher: Name - $name, Age - $age, Subject - $subject");
    }
}