用java代码实现在上次类与对象习题的基础上再扩展。创建一个student类，类内含有姓名、性别和年龄等成员变量，定义获取各变量的方法和思考方法; 创建一个teacher类，类内含有姓名、性别和年龄等成员变量，定义获取各变量的方法和教学方法；创建一个people类，声明两个成员变量分别是student类和teacher类的对象，定义获取student类和teacher类中成员变量及思考和教学的方法；创建一个主类，主类中创建一个student对象，一个teacher对象和一个people对象。输出对象的相关信息。

以下是用Java代码实现在上次类与对象习题的基础上再扩展的答案：

class Student {
    // 成员变量
    private String name;
    private String gender;
    private int age;

    // 构造函数
    public Student(String name, String gender, int age) {
        this.name = name;
        this.gender = gender;
        this.age = age;
    }

    // 获取成员变量的方法
    public String getName() {
        return name;
    }

    public String getGender() {
        return gender;
    }

    public int getAge() {
        return age;
    }

    // 定义思考方法
    public void think() {
        System.out.println("I am thinking...");
    }
}

class Teacher {
    // 成员变量
    private String name;
    private String gender;
    private int age;

    // 构造函数
    public Teacher(String name, String gender, int age) {
        this.name = name;
        this.gender = gender;
        this.age = age;
    }

    // 获取成员变量的方法
    public String getName() {
        return name;
    }

    public String getGender() {
        return gender;
    }

    public int getAge() {
        return age;
    }

    // 定义教学方法
    public void teach() {
        System.out.println("I am teaching...");
    }
}

class People {
    // 成员变量
    private Student student;
    private Teacher teacher;

    // 构造函数
    public People(Student student, Teacher teacher) {
        this.student = student;
        this.teacher = teacher;
    }

    // 获取成员变量的方法
    public Student getStudent() {
        return student;
    }

    public Teacher getTeacher() {
        return teacher;
    }

    // 定义获取student类和teacher类中成员变量的方法
    public String getStudentName() {
        return student.getName();
    }

    public String getStudentGender() {
        return student.getGender();
    }

    public int getStudentAge() {
        return student.getAge();
    }

    public String getTeacherName() {
        return teacher.getName();
    }

    public String getTeacherGender() {
        return teacher.getGender();
    }

    public int getTeacherAge() {
        return teacher.getAge();
    }

    // 定义思考和教学的方法
    public void think() {
        student.think();
    }

    public void teach() {
        teacher.teach();
    }
}

public class Main {
    public static void main(String[] args) {
        Student student = new Student("John", "Male", 18);
        Teacher teacher = new Teacher("Mary", "Female", 35);
        People people = new People(student, teacher);

        // 输出对象的相关信息
        System.out.println("Student name: " + people.getStudentName());
        System.out.println("Student gender: " + people.getStudentGender());
        System.out.println("Student age: " + people.getStudentAge());
        System.out.println("Teacher name: " + people.getTeacherName());
        System.out.println("Teacher gender: " + people.getTeacherGender());
        System.out.println("Teacher age: " + people.getTeacherAge());

        // 调用思考和教学的方法
        people.think();
        people.teach();
    }
}

输出结果为：

Student name: John
Student gender: Male
Student age: 18
Teacher name: Mary
Teacher gender: Female
Teacher age: 35
I am thinking...
I am teaching...