better shuffle

import java.util.*;
public class Deck {

    public class Card implements Comparable<Card> {
        private int value;
        Card(int v) {
            value = v;
        }
        public int getValue() {return value;}
        public String toString(){
            return ""+value;
        }
        public int compareTo(Card other) {
            return value - other.value;
        }
    }

    private final int num=52;
    Vector<Card> deck = new Vector<Card>();

    public Vector<Card> shuffle(Vector<Card> deck){
        if (deck == null || deck.size() < num) {
            System.out.println("\ninitialize deck");
            deck = new Vector<Card>(); // new deck
            for (int i=0; i<num; i++) {
                Card c = new Card(i);
                deck.add(c);
            }
        }
        int [] arr = new int[num];
        int j=0;
        for (Card card : deck) {
            arr[j++] = card.getValue();
        }
        shuffleArr(arr);
        deck = new Vector<Card>(); // new deck
        for (int i=0; i<num; i++) {
            Card c = new Card(arr[i]);
            deck.add(c);
        }
        return deck;
    }
    Random rand = new Random();
    public void shuffleArr(int [] arr){
        for (int i=0; i<arr.length-1; i++) {
            int rnd = i+ rand.nextInt(arr.length-i);
            //swap arr[i] and a[rnd]
            int tmp = arr[i];
            arr[i] = arr[rnd];
            arr[rnd] = tmp;
        }
    }

    public static void main(String[] args) {
        Deck deckInst = new Deck();
        Vector<Card> deck = null;
        for (int i=0; i<6; i++) {
            deck = deckInst.shuffle(deck);
            System.out.println("\nout:");
            for (Card card : deck) {
                System.out.print(","+card.toString());
            }
        }
        System.out.println("\nsorted:");
        Collections.<Card>sort(deck);
        for (Card card : deck) {
            System.out.print(","+card.toString());
        }
    }
}