Right now, the source for sun.net.www.protocol.jar.JarFileFactory is maintained in OS specific locations of the JDK repo:

Unix: src/java.base/unix/classes/sun/net/www/protocol/jar/JarFileFactory.java
Windows: src/java.base/windows/classes/sun/net/www/protocol/jar/JarFileFactory.java

Looking at the difference in these files, the only difference is a mere additional method (and usage of that method) on Windows. Instead of keeping two separate files with all the duplicate code, it would be easier to just move the source to "share/classes" and implement a conditional check for additional logic on Windows OS.

The entire side-by-side diff of these 2 files is attached for reference.