Delete file contents using RandomAccessFile

Question

I have a file which contains lot of zeros and as per the requirement the zeros in the file are invalid. I am using RandomAccessFile api to locate data in the file. Is there way so that all the zeros can be removed from the file using the same api.

Answer 1

You'll have to stream through the file and write out the content, minus the zeros, to a separate temporary file. You can then close and delete the original and rename the new file to the old file name. That's your best alternative for this particular use case.

Answer 2

You can use RandomAccessFile to read the files' data, and when you reach a point where you need to change the data you can overwrite the existing number of bytes with equal number of bytes. It's iff the new value is exactly the same length as the old value.

With RandomAccessFile its difficult and equally complex when the size of two, the one being changed and the new value are different. It involves a lot of seeks, reads and writes to move data back

Try to read the whole file, change the bits you have to change and write a new file. You might process one line at a time or read the whole file into memory, modify it and write it all back out again. It is a good idea to perform the edit in the following manner:

1. Read file
2. Write to Temporary File [just to back-up]
3. Rename original to back-up
4. Work on Temporary file.
5. Remove Backup if you were successful.