Jumping to a line and reading it

Question

I have to work with big files (many GB) and need quick lookups to retrieve specific lines on request.

The idea has been to maintain a mapping:

some_key -> byte_location

Where the byte location represents where in the file the line starts.

Edit: the question changed a little bit:

First I used:

FileInputStream stream = new FileInputStream(file);
BufferedReader reader = new BufferedReader(new InputStreamReader(stream));
FileChannel channel = stream.getChannel();

I noticed that FileChannel.position() will not return the exact position where the reader is currently reading because it is a "buffered" reader. It reads chunks of a given size (16k here) so what I get from the FileChannel is a multiple of 16k, and not the exact position where the reader is actually reading.

PS: the file is in UTF-8

Answer 1

Any reason not to create a FileInputStream, call stream.skip(pos) and then create an InputStreamReader around that, and a BufferedReader around the InputStreamReader?