定义一个接口Person，声明相关的属性和方法，再用Teacher类和Student类去继承这个接口

好的，以下是接口Person的定义：

public interface Person {
    String getName(); // 获取姓名
    int getAge(); // 获取年龄
    void setName(String name); // 设置姓名
    void setAge(int age); // 设置年龄
}

接下来是Teacher类和Student类的定义：

public class Teacher implements Person {
    private String name;
    private int age;
    private String subject;

    public Teacher(String name, int age, String subject) {
        this.name = name;
        this.age = age;
        this.subject = subject;
    }

    public String getSubject() {
        return subject;
    }

    public void setSubject(String subject) {
        this.subject = subject;
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public int getAge() {
        return age;
    }

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

    @Override
    public void setAge(int age) {
        this.age = age;
    }
}

public class Student implements Person {
    private String name;
    private int age;
    private String major;

    public Student(String name, int age, String major) {
        this.name = name;
        this.age = age;
        this.major = major;
    }

    public String getMajor() {
        return major;
    }

    public void setMajor(String major) {
        this.major = major;
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public int getAge() {
        return age;
    }

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

    @Override
    public void setAge(int age) {
        this.age = age;
    }
}

Teacher和Student类都实现了Person接口，并且实现了接口中的方法。这样可以保证Teacher和Student都拥有Person接口中定义的属性和方法。