定义一个Person类，含：姓名、性别、年龄等字段；设计Teacher类继承Person类，增加：职称、部门等字段；设计Student类继承Person类，增加：学号、班级等字段。定义各类的构造方法和toString(）方法，并分别创建对象进行测试。

在Java中，你可以按照以下步骤定义这些类：

// 定义 Person 类
public class Person {
    private String name;
    private String gender;
    private int age;

    // 默认构造器
    public Person() {}

    // 具体构造器接受参数
    public Person(String name, String gender, int age) {
        this.name = name;
        this.gender = gender;
        this.age = age;
    }

    // toString 方法返回个人信息字符串
    @Override
    public String toString() {
        return "Name: " + name + ", Gender: " + gender + ", Age: " + age;
    }
}

// Teacher 类继承自 Person 类并添加新字段和构造器
public class Teacher extends Person {
    private String title;
    private String department;

    // Teacher 类的构造器
    public Teacher(String name, String gender, int age, String title, String department) {
        super(name, gender, age); // 调用父类的构造器
        this.title = title;
        this.department = department;
    }

    // toString 方法扩展父类的方法
    @Override
    public String toString() {
        return super.toString() + ", Title: " + title + ", Department: " + department;
    }
}

// Student 类同样继承自 Person 类并添加新字段和构造器
public class Student extends Person {
    private String studentID;
    private String className;

    // Student 类的构造器
    public Student(String name, String gender, int age, String studentID, String className) {
        super(name, gender, age);
        this.studentID = studentID;
        this.className = className;
    }

    // toString 方法扩展父类的方法
    @Override
    public String toString() {
        return super.toString() + ", Student ID: " + studentID + ", Class: " + className;
    }
}

现在你可以使用这些类来创建对象并调用 `toString` 方法进行测试：

public static void main(String[] args) {
    // 创建一个 Teacher 对象
    Teacher teacher = new Teacher("John Doe", "Male", 35, "Professor", "Mathematics");

    // 创建一个 Student 对象
    Student student = new Student("Jane Smith", "Female", 18, "1001", "Science 1A");

    // 打印他们的信息
    System.out.println(teacher);
    System.out.println(student);
}