JAva list汎用ページング方法

/**      
pageNum:   
pageSize：      
**/
public static List startPageForCouponSorting(List list, Integer pageNum,Integer pageSize) {
    if (list == null) {
        return null;
    }
    if (list.size() == 0) {
        return null;
    }

    Integer count = list.size(); //     
    Integer pageCount = 0; //   
    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;
    }
    if(fromIndex>=count){
        return null;
    }
    List pageList = list.subList(fromIndex, toIndex);

    return pageList;
}