How to estimate zip file size in java before creating it

Question

I am having a requirement wherein i have to create a zip file from a list of available files. The files are of different types like txt,pdf,xml etc.I am using java util clas

Answer 1

+1 for Colin Herbert: Add files one by one, either back up the previous step or removing the last file if the archive is to big. I just want to add some details:

Prediction is way too unreliable. E.g. a PDF can contain uncompressed text, and compress down to 30% of the original, or it contains already-compressed text and images, compressing to 80%. You would need to inspect the entire PDF for compressibility, basically having to compress them.

You could try a statistical prediction, but that could reduce the number of failed attempts, but you would still have to implement above recommendation. Go with the simpler implementation first, and see if it's enough.

Alternatively, compress files individually, then pick the files that won't exceedd 5 MB if bound together. If unpacking is automated, too, you could bind the zip files into a single uncompressed zip file.