定义一个Person类，含：姓名、性别、年龄等字段；继承Person类设计Teacher类，增加：职称、部门等字段；继承Person类设计 Student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。

首先，我们定义一个基础的`Person`类，包含姓名、性别和年龄字段：

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

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

    // toString()方法用于获取Person对象的简单描述
    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", gender='" + gender + '\'' +
                ", age=" + age +
                '}';
    }
}

然后，我们设计`Teacher`类，它继承自`Person`并添加了职称和部门字段：

public class Teacher extends Person {
    private String title;
    private String department;

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

    @Override
    public String toString() {
        return "Teacher{" +
                super.toString() +
                ", title='" + title + '\'' +
                ", department='" + department + '\'' +
                '}';
    }
}

接着，我们设计`Student`类，同样继承自`Person`并增加了学号和班级字段：

public class Student extends Person {
    private String studentId;
    private String className;

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

    @Override
    public String toString() {
        return "Student{" +
                super.toString() +
                ", studentId='" + studentId + '\'' +
                ", className='" + className + '\'' +
                '}';
    }
}

现在我们可以创建这些类的对象进行测试：

public static void main(String[] args) {
    Person person = new Person("John", "Male", 30);
    System.out.println(person);

    Teacher teacher = new Teacher("Jane", "Female", 45, "Professor", "Math Department");
    System.out.println(teacher);

    Student student = new Student("Alice", "Female", 18, "12345", "Class A");
    System.out.println(student);
}

运行这段代码，你会看到每个对象的详细信息。