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类代码：

public class Person {
    protected String name;
    protected int age;
    protected char gender;

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

    public void eat() {
        System.out.println(name + " is eating.");
    }

    public void sleep() {
        System.out.println(name + " is sleeping.");
    }
}

Student类代码：

public class Student extends Person {
    private int grade;

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

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

Teacher类代码：

public class Teacher extends Person {
    private String subject;

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

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

TestOne类代码：

public class TestOne {
    public static void main(String[] args) {
        Person person = new Person("Tom", 20, 'M');
        Student student = new Student("Bob", 18, 'M', 10);
        Teacher teacher = new Teacher("Mary", 30, 'F', "Math");

        person.eat();
        person.sleep();

        student.eat();
        student.sleep();
        student.study();

        teacher.eat();
        teacher.sleep();
        teacher.teach();
    }
}

输出结果：

Tom is eating.
Tom is sleeping.
Bob is eating.
Bob is sleeping.
Bob is studying in grade 10.
Mary is eating.
Mary is sleeping.
Mary is teaching Math.