Java Programming

hi am a first time java user and i have this piece of code and when i build it it puts[void setDateOfBirth(String string) {
throw new UnsupportedOperationException("Not yet implemented");
}
at the bottom of page
could anyone say y?

package DoctorsSurgery;

import java.util.Collection;
import java.util.Date;
import java.util.Vector;
import DoctorsSurgery.Address;
import DoctorsSurgery.Doctor;
import DoctorsSurgery.Manager;
import DoctorsSurgery.Contact;



public class Patient implements Contact{
private String firstname;
private String lastname;
private Date dateOfBirth;
private Address address;
private int patientNo;




//association to doctor
public Doctor doctor;



//association to manager
public Manager manager;

//association to many bookings
public Collection bookings;

//aggregation to many prescriptions
public Collection prescriptions = new Vector();



private Address Addresss;

/** Creates a new instance of Patient */
public Patient() {
}

public String getFirstname() {
return firstname;
}

public void setFirstname(String firstname) {
this.firstname = firstname;
}

public String getLastname() {
return lastname;
}

public void setLastname(String lastname) {
this.lastname = lastname;
}

public Date getDateOfBirth() {
return dateOfBirth;
}

public void setDateOfBirth(Date dateOfBirth) {
this.dateOfBirth = dateOfBirth;
}

public int getPatientNo() {
return patientNo;
}

public void setPatientid(int patientid) {
this.patientNo = patientNo;
}

public Address getAddress() {
return address;
}

public void setAddress(Address address) {
this.address = address;
}

public String toString(){
return "["+firstname+" "+lastname+" "+dateOfBirth+" "+patientNo+" "+address+" ]";
}

void setDateOfBirth(String string) {
throw new UnsupportedOperationException("Not yet implemented");
}




}