SIMPLE RMI PROB

Question

I have created a very simple rmi test class passing a bk obkect to a remote library class - the code is below but i keep getting the oops error as specified in the client class - any ideas would be appreciated.
public class bk{
String st;
public bk(String s){
st=s;
import java.rmi.*;
public interface libint extends Remote{
public void addbook(bk b)throws RemoteException;
import java.rmi.*;
import java.rmi.server.*;
import java.util.*;
public class lib extends UnicastRemoteObject implements libint{
Vector v;
public lib()throws RemoteException{
Vector v = new Vector();
System.out.println("lib created");
public void addbook(bk b){
v.add(b);
System.out.println("BOOK ADDED");
import java.rmi.Naming;
public class Server{
public static void main(String args[]){
try{
Naming.rebind("libs", new lib());
System.out.println("System ready");
catch(Exception e){}
import java.rmi.Naming;
public class client{
public static void main(String args[]){
try{
bk b = new bk("john");
libint li = (libint)Naming.lookup("//127.0.0.1/libs");
li.addbook(b);
}catch(Exception e){System.out.println("oops2");}

Answer 1

I kind of guessed it was something to do with the addbook method but i have no idea why - any suggestions would again be welcome - cheers
java.lang.NullPointerException
at lib.addbook(lib.java:15)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.rmi.server.UnicastServerRef.dispatch(Unknown Source)
at sun.rmi.transport.Transport$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Unknown Source)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknown Source)
at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source)
at sun.rmi.server.UnicastRef.invoke(Unknown Source)
at lib_Stub.addbook(Unknown Source)
at client.main(client.java:8)