CODEWITHSUNDEEP
java
Paula Chittaro
Paula Chittaro

Reputation: 181

Find a String in a 10k line files in Java efficiently

I need to check if the password that an user entered is contained in a 10k lines .txt file that is locally stored in my computer. I've been asked to do this for a college project and they've been very emphatic about achieving this in an efficent manner, not taking too long to find the match.

The thing is that reading the file line by line using a BufferedReader the match is done almost instantly.

I've tested it in two computers, one with an ssd and the other one with an hdd and I cannot tell the difference.

Am I missing something? Is there another and more efficent way to do it? For example I could load the file or chunks of the file into memory, but is it worth it?

Upvotes: 0

Views: 106

Answers (1)

knittl
knittl

Reputation: 265946

10k passwords isn't all that much and should easily fit in RAM. You can read the file into memory when your application starts and then only access the in-memory structure. The in-memory structure could even be parsed to provide more efficient lookup (i.e. using a HashMap or HashSet) or sort it in memory for the one-time cost of O(n × log n) to enable binary-searching the list (10k items can be searched with max. 14 steps). Or you could use even fancier data structures such as a bloom filter.

Just keep in mind: when you write "it is almost instant", then it probably already is efficient enough. (Again, 10k passwords isn't all that much, probably the file is only ~100kB in size)

Upvotes: 2

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