用java实现创建一个 Person 类(父类)，通过扩展创建 Student 和 Teacher 类(子类);并在主类 TestOne 里实现创建对象，成员变量的初始化、 方法调用等;

Person类：

public class Person {
    private String name;
    private int age;

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

    public void speak() {
        System.out.println("My name is " + name + ", I am " + age + " years old.");
    }
}

Student类：

public class Student extends Person {
    private int grade;

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

    public void study() {
        System.out.println("I am studying in grade " + grade);
    }
}

Teacher类：

public class Teacher extends Person {
    private String subject;

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

    public void teach() {
        System.out.println("I am teaching " + subject);
    }
}

TestOne类：

public class TestOne {
    public static void main(String[] args) {
        Person p1 = new Person("Tom", 18);
        p1.speak(); // My name is Tom, I am 18 years old.

        Student s1 = new Student("Jack", 16, 10);
        s1.speak(); // My name is Jack, I am 16 years old.
        s1.study(); // I am studying in grade 10.

        Teacher t1 = new Teacher("Lucy", 30, "Java");
        t1.speak(); // My name is Lucy, I am 30 years old.
        t1.teach(); // I am teaching Java.
    }
}