Home/ Questions/Q 6878461
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-27T04:43:36+00:00

I have a rather large text file (~4m lines) I’d like to parse and

  • 0

I have a rather large text file (~4m lines) I’d like to parse and I’m looking for advice about a suitable data structure in which to store the data. The file contains lines like the following:

Date        Time    Value
2011-11-30  09:00   10
2011-11-30  09:15   5
2011-12-01  12:42   14
2011-12-01  19:58   19
2011-12-01  02:03   12

I want to group the lines by date so my initial thought was to use a TreeMap<String, List<String>> to map the date to the rest of the line but is a TreeMap of Lists a ridiculous thing to do? I suppose I could replace the String key with a date object (to eliminate so many string comparisons) but it’s the List as a value that I’m worried might be unsuitable.

I’m using a TreeMap because I want to iterate the keys in date order.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    is a TreeMap of Lists a ridiculous thing to do?

    Conceptually not, but it is going to be very memory-inefficient (both because of the Map and because of the List). You’re looking at an overhead of 200% or more. Which may or may not be acceptable, depending on how much memory you have to waste.

    For a more memory-efficient solution, create a class that has fields for every column (including a Date), put all those in a List and sort it (ideally using quicksort) when you’re done reading.

    • 0