冒泡和随机排序

冒泡：    其实就是把一个数组里的数据颠倒一下

public static String[] loopRank(String[] bookIDs, int num)
    {
        if (null != bookIDs && 0 != bookIDs.length)
        {
            if (num >= bookIDs.length)
            {
                num = 1;
            }
            
            int length = bookIDs.length;
            String[] temp = new String[length];
            System.arraycopy(bookIDs, length - num, temp, 0, num); //源数组、源数组要复制的起始位置、目标数组、目标数组要复制的起始位置、要复制的长度
            System.arraycopy(bookIDs, 0, temp, num, length - num);
            return temp;
        }
        else
        {
            return bookIDs;
        }
    }

随机：

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;
        }
    }

private 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;
    }