虚拟字段进行排序后分页

遇到排序后分页是，会在sql中继续宁排序，用PageHelper进行分页。但如果是java代码里的虚拟字段排序，程序的分页自然在排序之前，排序时只是对这一页（limit）进行排序，并不完整，因此，需要自己写一个简单的list分页

    public static List startPage(List list, Integer pageNum, Integer pageSize) {
        if (list == null) {
            return null;
        }
        if (list.size() == 0) {
            return null;
        }
        Integer count = list.size(); // 记录总数
        Integer pageCount = 0; // 页数
        if (count % pageSize == 0) {
            pageCount = count / pageSize;
        } else {
            pageCount = count / pageSize + 1;
        }
        int fromIndex = 0;
        int toIndex = 0;
        if (pageNum != pageCount) {
            fromIndex = (pageNum - 1) * pageSize;
            toIndex = fromIndex + pageSize;
        } else {
            fromIndex = (pageNum - 1) * pageSize;
            toIndex = count;
        }
        List pageList = list.subList(fromIndex, toIndex);
        return pageList;
    }

使用

        resultsList = OtherUtils.startPage(resultsList,pageNum,pageSize);

        JSONObject resultObject = new JSONObject();
        resultObject.put("content",resultsList);
        resultObject.put("pageNum",pageNum);
        resultObject.put("pageSize",pageSize);
        Double totalPages = Double.valueOf(resultsList.size())/Double.valueOf(pageSize);
        resultObject.put("totalPages",(int)Math.ceil(totalPages));
        resultObject.put("totalSize",resultsList.size());