If you see this error while trying to pack files, it means Zip4j believes you are trying to append files to a broken, pre-existing archive. File.createNewFile() If you are initializing the zip file pointer, .createNewFile() beforehand. Let Zip4j handle the file creation on its own:
It sounds obvious, but often a file has a .zip extension despite being a renamed PDF, text file, or corrupted image. If the internal structure doesn't match the ZIP specification, Zip4j will reject it. 2. File Corruption or Incomplete Downloads If you see this error while trying to
This comprehensive guide breaks down why this happens and provides actionable solutions depending on whether you are reading/extracting writing/creating a zip file. 🔍 Understanding the Root Causes If the internal structure doesn't match the ZIP
Verify the actual file format. If it’s an HTML error page (e.g., from a failed download), re-download the file. 🔍 Understanding the Root Causes Verify the actual
Get-Content archive.zip -TotalCount 1 -Encoding Byte | Format-Hex
The file starts with EF BB BF (UTF-8 BOM) or a stray null byte before PK .
Last updated: 2025 – Works with Zip4j versions 2.10.x and above.