Creating zip archive in Java

Question

I have one file created by 7zip program. I used deflate method to compress it. Now I want to create the same archive (with the same MD5sum) in java

Answer 1

Just to clarify, you used the ZIP algorithm in 7zip for your original? Also 7zip claims to have a 2-10% better compression ratio than other vendors. I would venture a guess that the ZIP algorithm built into Java is not nearly as optimized as the one in 7zip. Your best best is to invoke 7zip from the command line if you want a similarly compressed file.

Are you trying to unpack a ZIP file, change a file within it, then re-compress it so that it has the same MD5 hash? Hashes are meant to prevent you from doing that.