Exception in thread "Thread-2" java.lang.NullPointerException

Question

public class AddRunnable implements Runnable{
private Scanner sc;
private ContactStore cs;
private Contact contact;
private String fn,ln,pn;
public AddRunnable(Scanner sc, ContactStore cs) {
    this.sc = sc;
    this.cs = cs;}
@Override
public void run() {
    System.out.println("INSERT First name: ");
    fn = sc.nextLine();
    System.out.println("INSERT Last name: ");
    ln = sc.nextLine();
    System.out.println("INSERT Phone number: ");
    pn = sc.nextLine();
    contact.setFirstName(fn);
    contact.setLastName(ln);
    contact.setPhoneNumber(pn);
    cs.add(contact);
    System.out.println("new ID is: " + contact.getId());
    System.out.println();
    System.out.println();}

main програма

switch (line) {
                case "add":
                    thread = new Thread(new AddRunnable(sc,cs));
                    thread.start();
                    thread.join();
                    break;

когда я запускаю и ввожу "add" ловит Exception

Exception in thread "Thread-5" java.lang.NullPointerException
at ge.gtu.java.hw326.runnables.AddRunnable.run(AddRunnable.java:23)
at java.lang.Thread.run(Thread.java:745)

что делать в чем ошибся?