已定义类型，怎么修改

错误显示已定义类型，应该怎么修改呀？

源代码
package zhangjie.zuoy;

public class Student {
/父类Student/

 String name;
 int age;
 Student(String name,int age){
  this.name=name;
  this.age=age;
 }
 public void show(){
  System.out.println("name:"+name+" "+"age:"+age);
 }
}
/*子类Undergraduate继承于父类Student*/
class Undergraduate extends Student{
 String degree;
 Undergraduate(String name,int age,String degree){
  super(name,age);
  this.degree=degree;
 }
 public void show(){
  System.out.println("name:"+name+" "+"age:"+age+" "+"degree:"+degree);
 }
}
public class Student {
 public static void main(String args[]){
  Student student=new Student("张三",16);//创建实例对象
  Undergraduate undergraduate=new Undergraduate("李四",20,"bechelor");//创建实例对象
  student.show();
  undergraduate.show();
 }
}

你一个文件里定义了两个Student类，而且都是public的，这明显是违反规则的

你在Student类里面又定义一个Student类？

类不要重复定义、
解决方法：22行的Student改个名字就好了