将三个代码片段整合成一个完整的程序代码？

当然可以。这是一个将三个代码片段整合成一个完整Java程序的例子，包括`Person`类及其子类`Student`和`Teacher`，以及主函数`main`来接收用户输入并输出相应的信息：

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

    // 构造方法
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    // getter and setter
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public int getAge() { return age; }
    public void setAge(int age) { this.age = age; }

    // toString方法
    @Override
    public String toString() {
        return "Name: " + name + ", Age: " + age;
    }
}

// 定义Student类
public class Student extends Person {
    private int electiveCourses;

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

    // getter for electiveCourses
    public int getElectiveCourses() { return electiveCourses; }
    // setter for electiveCourses (省略，因为已经有了默认的setter)

    // override toString to include elective courses
    @Override
    public String toString() {
        return super.toString() + ", Elective Courses: " + electiveCourses;
    }
}

// 定义Teacher类
public class Teacher extends Person {
    private String teachingSubject;

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

    // getter for teachingSubject
    public String getTeachingSubject() { return teachingSubject; }
    // setter for teachingSubject (省略，因为已经有了默认的setter)

    // override toString to include teaching subject
    @Override
    public String toString() {
        return super.toString() + ", Teaching Subject: " + teachingSubject;
    }
}

// 主函数
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.println("请输入人员类型（Teacher或Student）:");
        String userType = scanner.next();

        switch (userType) {
            case "Student":
                System.out.println("请输入姓名 年龄 选修课程数: ");
                String[] studentInfo = scanner.nextLine().split(" ");
                String studentName = studentInfo[0];
                int studentAge = Integer.parseInt(studentInfo[1]);
                int studentCourses = Integer.parseInt(studentInfo[2]);

                Student student = new Student(studentName, studentAge, studentCourses);
                System.out.println(student.toString());
                break;
            case "Teacher":
                System.out.println("请输入姓名 年龄 教授课程: ");
                String[] teacherInfo = scanner.nextLine().split(" ");
                String teacherName = teacherInfo[0];
                int teacherAge = Integer.parseInt(teacherInfo[1]);
                String teacherSubject = teacherInfo[2];

                Teacher teacher = new Teacher(teacherName, teacherAge, teacherSubject);
                System.out.println(teacher.toString());
                break;
            default:
                System.out.println("无效的类型");
                break;
        }

        scanner.close();
    }
}

这个程序会根据用户的输入，创建对应的`Student`或`Teacher`对象，并打印出相关信息。如果输入的是其他类型，则会显示错误消息。