随机生成n张扑克牌。

• 开发提示：

  • 使用集合保存所有的扑克牌对象。
  • 从所有牌中，随机移除n张牌，保存到新集合。
  • 判断n的值，不能超越一副扑克牌的范围。

• 参考答案：

	public class Test6 {
	    public static void main(String[] args) {
	        int n = 5;
	        ArrayList<Card> cards = randomCard(n);
	
	        if (cards != null) {
	            System.out.println("随机"+ n +"张牌:" );
	            for (int i = 0; i < cards.size(); i++) {
	                Card card = cards.get(i);
	                card.showCard();
	            }
	        }else {
	            System.out.println(n+"超越范围,无法获取牌" );
	        }
	
	        System.out.println();
	        System.out.println();
	        int n2 = 55;
	        ArrayList<Card> cards2 = randomCard(n2);
	
	        if (cards2 != null) {
	            System.out.println("随机"+ n2 +"张牌:" );
	            for (int i = 0; i < cards.size(); i++) {
	                Card card = cards.get(i);
	                card.showCard();
	            }
	        }else {
	            System.out.println("随机"+ n2 +"张牌:
超越范围,无法获取" );
	        }
	    }
	    public static ArrayList<Card> randomCard(int n) {
	        if (n > 54 || n < 0)
	            return null;
	
	        ArrayList<Card> rList = new ArrayList<>();
	        ArrayList<Card> cards = allCard();
	
	        Random r = new Random();
	        for (int i = 0; i < n; i++) {
	            int index = r.nextInt(cards.size());
	            Card rCard = cards.remove(index);//我认为全文最高明的地方在此（52张牌做到没有重复使用，且不用写那么多避免重复的代码），当remove掉一个时，返回值add到rList中，size随之减小
	            rList.add(rCard);
	        }
	        return rList;
	    }
	
	    public static ArrayList<Card> allCard() {
	        ArrayList<Card> allList = new ArrayList<>();
	        // 花色数组
	        String[] hs = {"黑桃", "红桃", "梅花", "方片"};
	        // 点数数组
	        String[] ds = {"A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K"};
	
	        for (int H = 0; H < hs.length; H++) {
	            for (int d = 0; d < ds.length; d++) {
	                Card card = new Card(hs[H], ds[d]);
	                // 添加到集合
	                allList.add(card);
	            }
	        }
	        return allList;
	    }
	}
	
	class Card {
	    private String ds; // 点数
	    private String hs; // 花色
	    public Card(String ds, String hs) {
	        this.ds = ds;
	        this.hs = hs;
	    }
	    public void showCard() {
	        System.out.print(ds + hs+" ");
	    }
	}