Java Fixed File Size operation

Question

In Java using RandomAccessFile I can create a file and then do setLength Now Assume I allocate length of 1024 bytes. Now I wrote say 512 bytes. Now again I want to write 256 bytes without changing size of the file and clearing those 512 bytes

I do not want to use setLength(0) in the middle of my process to avoid java.io.IOException: No space left on device

score 4 · Answer 1 · answered Oct 08 '13 at 17:16

4

You can use seeks:

file.setLength(1024);
file.write(new byte[512]); //or some other 512 bytes
//close and reopen later
file.seek(512);
//write 256 more bytes

Edit: I don't think you're realizing the spirit of RandomAccessFile. You can create it to be 512 bytes and keep writing to it so it can extend implicitly without setLength calls.

answered Oct 08 '13 at 17:16

nanofarad

40,330
4
86
117

//write 256 more bytes this is what i want to wipe out previously written 512 bytes and write fresh 256 bytes – Avinash Oct 08 '13 at 17:22
@Avinash ok, seek(0) and then write. – Peter Lawrey Oct 08 '13 at 17:48
seek(offset) sets the location in the file where the next read or write starts from. seek(0) resets to the beginning of the file. seek(512) moves 512 bytes into the file. – ChuckCottrill Oct 08 '13 at 18:10
See: http://stackoverflow.com/questions/9671126/how-to-read-a-file-from-a-certain-offset – ChuckCottrill Oct 08 '13 at 18:11
seek(), read(), write(), getFilePointer(), see: http://qdaolong.blogspot.com/2013/02/offset-of-file-in-c-and-java.html – ChuckCottrill Oct 08 '13 at 18:22

Java Fixed File Size operation

1 Answers1