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Index › Programming Questions & Help › Programs › File - Random Access
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File - Random Access ? (Read 486 times)
alphachapmtl
File - Random Access ?
Mar 16th, 2008, 2:17am  
Is there a way to go directly to the last element of a file ?

It's a huge text file of integer, one integer per line, more than 100 million lines.
Is there a fast way to find the last element of the file?
Right now I use a BufferedReader, and I scan the whole file line by line from start to end.
I have
BufferedReader br = new BufferedReader(new FileReader(f));
and I do
while (br.ready())
 br.readLine()
 ...

Is there a better way?
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« Last Edit: Mar 17th, 2008, 2:34am by alphachapmtl »  
 
fry
Re: File - Last element ?
Reply #1 - Mar 16th, 2008, 4:32pm  
use RandomAccessFile from Java:
http://java.sun.com/j2se/1.4.2/docs/api/java/io/RandomAccessFile.html
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WWW  
blueberry151
Re: File - Random Access ?
Reply #2 - Mar 25th, 2008, 9:18am  
Wow how long does that take?
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alphachapmtl
Re: File - Random Access ?
Reply #3 - Mar 25th, 2008, 6:03pm  
It takes almost 15 min to scan the file that way.

I'm now changing my code,  
from using a BufferedReader(FileReader()),
to using a RandomAccessFile().

That way I can get the #integers in the file without scanning the whole file,
----  ff = new File(fname);
----  raf = new RandomAccessFile(ff, "r");
----  count = (int)(raf.length()/4);

and I can quickly read the last element this way:
----  raf.seek(raf.length()-4);
----  n = raf.readInt()

It's not all done yet. I'm learning Java so everything I do takes longer than it should.
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