bytes[] getIV() method is returning null value

I’m writing a code which will encrypt and decrypt the message(using DES algorithm), and both messages will be displayed in Dialog box. But when i run the code i got nullPointerException. And after debugging the code i realize the null data is getting stored ‘iv’.
Here is my code:-

import javax.crypto.spec.*;
import javax.crypto.*;
import javax.swing.*;
public class des 
    public static void main(String ar[]) throws Exception
        KeyGenerator keygen=KeyGenerator.getInstance("DES");
        SecretKey secretkey=keygen.generateKey();
        Cipher cip=Cipher.getInstance("DES");

        String inputText=JOptionPane.showInputDialog("Give input:");

        byte[] iv=cip.getIV();
        IvParameterSpec ps=new IvParameterSpec(iv);

        byte[] encrypted=cip.doFinal(inputText.getBytes());

        byte[] decrypted=cip.doFinal(encrypted);

        JOptionPane.showMessageDialog(null,"Encrypted :"+new String(encrypted)+"n Decrypted :"+new String(decrypted));