在Java中对CSV文件进行读写操作的代价是多少？

Question

I am writing a software which has a part dealing with read and write operaions. I am wondering how costly these operations are on a csv file. Is there are any other file formats that consume less time? Because I have to do write and read on csv files at the end of every cycle.

Answer 1

Read and write operations depend on the file system, hardware, software configuration, memory, mermory setup and size of the file to read. But not on the format. A different problem related with this is the cost of parsing the file that surely must relative low as csv is very simple.

The point is that CSV is a good format for tables of data but not for nested data. If your data has a lot of nested information you can separate it into different csv files or you will have some information redundancy that will penalize your performance. But other formats might have other kind of redundancy.

And do not optimize prematurily. If you are reading and writing from the file very frecuently this file will surely be kept on RAM. JSON or a zipped file might save size and be read faster but would have a higher parsing time and could be even slower at the end. And the parsing time depends also on the implemenation of the library (Gson vs Jackson) and version.

It will be nice to know the reasons behind your problem to give better ansewrs.

Answer 2

The cost of reading / writing to a CSV file, and whether it is suitable for your application, depend on the details of your use case. Specifically, if you are simply reading from the beginning of the file and writing to the end of the file, then the CSV format is likely to work fine. However, if you need to access particular records in the middle of your file then you probably wish to choose another format.

The main issue with a CSV file is that it is not a good format choice for random access, since each record (row) is of variable size, so you cannot simply seek to a particular record offset in the file, and instead need to read every row (well, you could still jump and sample, but you cannot seek directly by record offset). Other formats with fixed sized records would allow you to seek directly to a particular record in the file, making updating of an entry in the middle of the file possible without needing to re-read and re-write the entire file.