FULL PRODUCT VERSION :
LANELSON-mac:~ LANELSON$ java -version
java version "1.8.0_74"
Java(TM) SE Runtime Environment (build 1.8.0_74-b02)
Java HotSpot(TM) 64-Bit Server VM (build 25.74-b02, mixed mode)
LANELSON-mac:~ LANELSON$ 


ADDITIONAL OS VERSION INFORMATION :
LANELSON-mac:test LANELSON$ uname -a
Darwin LANELSON-mac 15.6.0 Darwin Kernel Version 15.6.0: Mon Aug 29 20:21:34 PDT 2016; root:xnu-3248.60.11~1/RELEASE_X86_64 x86_64


A DESCRIPTION OF THE PROBLEM :
If you supply a URLClassLoader with only one URL like this:

  jar:file:/some/file.jar!/

...and file.jar is located in a directory with extra.jar, and file.jar's META-INF/MANIFEST.MF resource has a Class-Path header like so:

  Class-Path: extra.jar

...the URLClassLoader will be unable to load classes found in extra.jar--that is, it does not respect file.jar's META-INF/MANIFEST.MF's Class-Path header.

However, if you supply the URLClassLoader with an equivalent URL like this:

  file:/some/file.jar

...while leaving everything else unchanged, the Class-Path header is processed correctly and the URLClassLoader can load classes found in extra.jar.

See http://stackoverflow.com/questions/39906038/does-urlclassloader-traverse-manifest-mf-class-path-headers-properly for a unit test.


REPRODUCIBILITY :
This bug can be reproduced always.