学生类，大学生类，研究生类

[java]代码库

import java.util.Scanner;
public class Main{
	public static void main(String[] args) {
         Scanner scan = new Scanner(System.in);
         int no = scan.nextInt();
         String name = scan.next();      
         String sex = scan.next();      
         Student s = new Student(no, name, sex);
         s.print();

         no = scan.nextInt();
         name = scan.next();      
         sex = scan.next();      
         String major = scan.next();
         CollegeStudent c = new CollegeStudent(no, name, sex, major);
         c.print();

         no = scan.nextInt();
         name = scan.next();      
         sex = scan.next();      
         major = scan.next();
         String supervisor = scan.next();
         GraduateStudent g = new GraduateStudent(no, name, sex, major, supervisor );
         g.print();
         g.doResearch();
         scan.close(); 
    }
} 

class Student{
	private int no;
	private String name;
	private String sex;
	public Student(int _no, String _name, String _sex){
		no = _no;
		name = _name;
		sex = _sex;
	}
	public int getNo() {
		return no;
	}
	public String getName() {
		return name;
	}
	public String getSex() {
		return sex;
	}
	public void print() {
		System.out.println("no: " + no + "\n" +"name: " +name +"\n" +"sex: " +sex );
	}
}
class CollegeStudent extends Student{
	private String major;
	public CollegeStudent(int _no, String _name, String _sex, String _major) {
		super(_no, _name, _sex);
		major = _major;
	}
	public int getNo() {
		return super.getNo();
	}
	public String getName() {
		return super.getName();
	}
	public String getSex() {
		return super.getSex();
	}
	public String getMajor() {
		return major;
	}
	public void print() {
		System.out.println("no: " +super.getNo()  + "\n" +"name: " +super.getName() +"\n" +"sex: " +super.getSex() +"\n" +"major: " +major );
	}
}
class GraduateStudent extends CollegeStudent{
	private String supervisor;
	public GraduateStudent(int _no, String _name, String _sex, String _major, String _supervisor) {
		super(_no, _name, _sex, _major);
		supervisor = _supervisor;
	}
	
	public void print() {
		System.out.println("no: " +super.getNo()  + "\n" +"name: " +super.getName() +"\n" +"sex: " +super.getSex() +"\n" +"major: " +super.getMajor() +"\n" + "supervisor: " +supervisor);
	}
	public void doResearch() {
		System.out.print(super.getName()+" is doing research");
	}
}