What is the maximum number of files per jar?

Question

I'd like to know if there is a maximum number of files allowed per jar, after which you can have classpath issues like classes not taken into account?

Answer 1

The jar format is just a rebranded zip format, so it inherits the limitations of that format.

The original zip format has a limit of 65535 entries, so in total in Java 6 and earlier, you can have at most that many classes or other files, combined. Many tools also include directories as entires, and this reduces the entires available for classes and other files.

In java 7, zip64 is supported, with a much higher limit.

I suspect the failure mode, however, won't be randomly missing files, but failure at jar generation time.

Answer 2

A .jar file is really just a .zip file with a special manifest. So the limits are the same as for .zip files

• Up to Java 6, normal zip files are supported, with a maximum of 4gb size and 65535 files
• From Java 7 onwards, zip64 format is supported with something like 16 exabyte capacity. this is effectively unlimited for normal use with current hardware (it's about the size of all the content on the internet)