内存分页

内存分页

 /**
     * <p>Description: 内存分页 </p>
     *
     * @param records  待分页的数据
     * @param pageNum  当前页码
     * @param pageSize 每页显示的条数
     * @return 分页之后的数据
     */
    public static <T> List<T> pagination(List<T> records, int pageNum, int pageSize) {
        if (CollectionUtils.isEmpty(records)) {
            return Collections.emptyList();
        }
        if (pageNum < 0 || pageSize < 0) {
            return Collections.emptyList();
        }
        int totalCount = records.size();
        int pageCount;
        int remainder = totalCount % pageSize;
        if (remainder > 0) {
            pageCount = totalCount / pageSize + 1;
        } else {
            pageCount = totalCount / pageSize;
        }
        log.info("总记录数为: [{}], 当前页码为: [{}], 每页显示的条数为: [{}]", totalCount, pageNum, pageSize);
        if (remainder == 0) {
            records = records.stream().skip((pageNum - 1) * pageSize).limit(pageSize * pageNum).collect(Collectors.toList());
            return records;
        } else {
            if (pageNum == pageCount) {
                records = records.stream().skip((pageNum - 1) * pageSize).limit(totalCount).collect(Collectors.toList());
                return records;
            } else {
                records = records.stream().skip((pageNum - 1) * pageSize).limit(pageSize * pageNum).collect(Collectors.toList());
                return records;
            }
        }
    }

集合拷贝

public static <T> List<T> depCopy(List<T> srcList) {
    ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
    try {
        ObjectOutputStream out = new ObjectOutputStream(byteOut);
        out.writeObject(srcList);

        ByteArrayInputStream byteIn = new ByteArrayInputStream(byteOut.toByteArray());
        ObjectInputStream inStream = new ObjectInputStream(byteIn);
        List<T> destList = (List<T>) inStream.readObject();
        return destList;
    } catch (IOException e) {
        e.printStackTrace();
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }
    return null;
}