静态变量和静态方法的上下引用

public class Libr{
class Book
{String name1;
 int num;
}
class Student{
     String name2;
     int id;
    String borrow(int date,Book a){
        return "studenst's name:"+name2+" student's id:"+id+" borrow date is"+date;
    }
   
}


String borrow(String name,int num){
   
    }
        
public static void main(String[] args){
    Book a=new Book(bww,1);
    Student b=new Student(hzh,2);
    int date=1025;
    System.out.println(b.borrow(date,a));
}
}