分页工具类，封装了结果集（使用泛型），查询记录数，第几页，每页多少条记录，总页数，上下首末页属性和方法。-Pagination tools, encapsulates the result set (using Generics) to query the number of records, the first few pages, the number of records per page, total pages, up and down the end of the first pag