一段关于获取随机数的代码

我觉得比较精妙吧。   注意，第一个参数不要比第二个参数大。

 

public static int[] randon(int num, int length)
    {
        boolean[] cards = new boolean[length];
        
        for (int r = 0; r < length; ++r)
        {
            cards[r] = false;
        }
        
        Random arg6 = new Random();
        int[] result = new int[num];
        
        for (int index = 0; index < num; ++index)
        {
            int x;
            do
            {
                x = arg6.nextInt(length);
            } while (cards[x]);
            
            cards[x] = true;
            result[index] = x;
        }
        
        return result;
    }

 

再来一段

 

public static String[] randomRank(String[] bookIDs, int num)
    {
        if (null != bookIDs && 0 != bookIDs.length)
        {
            if (num >= bookIDs.length)
            {
                num = bookIDs.length;
            }
            
            ArrayList list = new ArrayList(bookIDs.length);
            
            for (int ran = 0; ran < bookIDs.length; ++ran)
            {
                list.add(bookIDs[ran]);
            }
            
            int[] arg6 = randon(num, bookIDs.length);
            ArrayList reList = new ArrayList(bookIDs.length);
            
            int ids;
            for (ids = 0; ids < arg6.length; ++ids)
            {
                String o = (String)list.get(arg6[ids]);
                reList.add(o);
            }
            
            for (ids = 0; ids < reList.size(); ++ids)
            {
                list.remove(reList.get(ids));
            }
            
            reList.addAll(list);
            String[] arg7 = new String[reList.size()];
            return (String[])((String[])reList.toArray(arg7));
        }
        else
        {
            return null;
        }
    }