Redis 分页

/**

* 请求不存在的页码时，返回最后一页的数据

*/

public static <T extends Comparable<T>> List<T> page(List<T> list, Integer pageNum, Integer pageSize) {

if (CollectionUtils.isEmpty(list)) {

return Collections.emptyList();

}

if (pageNum == null || pageSize == null) {

return list;

}

int totalRows = list.size();

if (pageSize < 0) {

pageSize = 10;

}

int totalPage = ((totalRows % pageSize) == 0) ? (totalRows / pageSize) : ((totalRows / pageSize) + 1);

if (pageNum <= 0) {

pageNum = 1;

} else if (pageNum > totalPage) {

pageNum = totalPage;

}

int offset = (pageNum - 1) * pageSize;

return list.stream().sorted(Comparator.reverseOrder()).skip(offset).limit(pageSize).collect(Collectors.toList());

}

/**

* 开始分页

*

* @param list

* @param pageNum 用户请求页码

* @param pageSize 每页多少条数据

* @return 请求不存在的页码时，返回page data为空

*/

public static List startPage(List list, Integer pageNum,

Integer pageSize) {

List<Object> pageList = new ArrayList<>();

if (CollectionUtils.isEmpty(list)) {

return pageList;

}

Integer count = list.size(); // 记录总数

Integer pageCount = 0; // 数据总页数

if (count % pageSize == 0) {

pageCount = count / pageSize;

} else {

pageCount = count / pageSize + 1;

}

int fromIndex = 0; // 开始索引

int toIndex = 0; // 结束索引

if (pageNum > pageCount) { // 用户请求页码 > 数据总页数时返回空数据

return pageList;

} else if (pageNum != pageCount) {

fromIndex = (pageNum - 1) * pageSize;

toIndex = fromIndex + pageSize;

} else {

fromIndex = (pageNum - 1) * pageSize;

toIndex = count;

}

pageList = list.subList(fromIndex, toIndex);

return pageList;

}