visibility modifier in java program

import java.util.Scanner;
class student
{
    public int er_no,sem;
    private int age;
    private String name;
    void set_age(int x)
    {
        age=x;
    }
    void set_name(String k)
    {
        name=k;
    }
    void get_data()
    {
        System.out.println("er_no "+er_no);
        System.out.println("sem "+sem);
        System.out.println("age "+age);
        System.out.println("name "+name);
    }
}

class faculty
{
    public String name;
    private String dept;
    void set_dept(String k)
    {
        dept=k;
    }
    void get_data()
    {
        System.out.println("faculty name "+name);
        System.out.println("faculty dept "+dept);
    }
}
public class Visibility {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        Scanner virus=new Scanner(System.in);
        student s=new student();
        System.out.println("enter er_no");
        s.er_no=virus.nextInt();
        System.out.println("enter sem");
        s.sem=virus.nextInt();
        System.out.println("enter name");
        String k=virus.next();
        s.set_name(k);
        System.out.println("enter age");
        int x=virus.nextInt();
        s.set_age(x);
        s.get_data();
        faculty f=new faculty();
        System.out.println("enter name of faculty");
        f.name=virus.next();
        System.out.println("enter dept");
        k=virus.next();
        f.set_dept(k);
        f.get_data();
    }
}