Please check the errors,if any,in this code...i am a java beginner

import java.util.ArrayList;

import java.util.Calendar;

import java.util.Date;

import java.util.HashMap;

import java.util.Map;

import java.util.Scanner;



public class Hospital
 {

    /**
     * @param args
     */

public static void main(String[] args)
 {

        // TODO Auto-generated method stub

Map<Integer,Patient> patients=new HashMap<Integer,Patient>();

PatientFunction pf=new PatientFunction();

Patient p1=new Patient();

Calendar c=Calendar.getInstance();

Date d=new Date();
d.setMonth(d.getMonth()-1);

c.setTime(d);

p1.setAge(25);
p1.setName("Arg");
p1.setLastAppointment(c);

patients.put(p1.getPatientId(), p1);

Scanner s=new Scanner(System.in);


int ctr=0;

do
{

System.out.println("::::::::Hospital::::::::");

System.out.println("Enter 1.Add a patient 2.Update Patient 3.Search patient 4.Display patients or View status");

ctr=s.nextInt();
s.nextLine();

switch(ctr)
{

case 1:

Patient p=pf.addPatient();

if(p==null)

System.out.println("Incorrect input");

else

patients.put(p.getPatientId(), p);

break;

case 2:

System.out.println("Enter a patient ID");

int pid=s.nextInt();
s.nextLine();

if(patients.containsKey(pid))
{

Patient p2=pf.updatePatient(patients.get(pid));

if(p2!=null)

patients.put(p2.getPatientId(), p2);

else

System.out.println("Invalid input");    

}

else

{

System.out.println("Patient with the ID does not exist");
                    }

break;

case 3:

System.out.println("Enter a patient ID");

pid=s.nextInt();
s.nextLine();

if(patients.containsKey(pid))
{

pf.displayPatientDetails(patients.get(pid));

                    }

else

{

System.out.println("Patient with the ID does not exist");
                    }

break;

case 4:

if(patients.size()==0)

System.out.println("No patients in list");

else

{   
ArrayList<Patient> al=new ArrayList<Patient>(patients.values());
                        pf.displayAll(al);              
                    }

break;

}

System.out.println("Continue? Enter y or n");

if(s.nextLine().toLowerCase().equals("y"))

ctr=999;

}
while(ctr==999);

}


}