Hi!
I'm experiencing multithreading issues with version 0.9.10.

With two threads accessing the same jar file i get the following Log Messages:
DEBUG Thread-1 2015-07-15 11:26:33,136 org.reflections.Reflections - going to scan these urls:
jar:file:/path/to/jar/myjar.jar!/
DEBUG Thread-2 2015-07-15 11:26:33,138 org.reflections.Reflections - going to scan these urls: ...
jar:file:/path/to/jar/myjar.jar!/
INFO Thread-1 2015-07-15 11:26:33,289 org.reflections.Reflections - Reflections took 153 ms to scan 3 urls, producing 207 keys and 529 values

Thread-2 crashes with this stack:

java.lang.IllegalStateException: zip file closed
at java.util.zip.ZipFile.ensureOpen(ZipFile.java:634)
at java.util.zip.ZipFile.access$200(ZipFile.java:56)
at java.util.zip.ZipFile$1.hasMoreElements(ZipFile.java:487)
at java.util.jar.JarFile$1.hasMoreElements(JarFile.java:241)
at org.reflections.vfs.ZipDir$1$1.computeNext(ZipDir.java:30)
at org.reflections.vfs.ZipDir$1$1.computeNext(ZipDir.java:26)
at com.google.common.collect.AbstractIterator.tryToComputeNext(AbstractIterator.java:143)
at com.google.common.collect.AbstractIterator.hasNext(AbstractIterator.java:138)
at org.reflections.Reflections.scan(Reflections.java:240)
at org.reflections.Reflections.scan(Reflections.java:204)
at org.reflections.Reflections.(Reflections.java:129)
at org.reflections.Reflections.(Reflections.java:170)
at org.reflections.Reflections.(Reflections.java:143)

The ZipDir seems to be created in DefaultUrlTypes.jarUrl.createDir(URL):
return new ZipDir(((JarURLConnection) urlConnection).getJarFile());

but sun.net.www.protocol.jar.JarURLConnection.getJarFile() uses (or may use) a cache:
this.jarFile = factory.get(getJarFileURL(), getUseCaches());

In my case both threads get the same instance of JarFile, and after the first thread has closed the ZipDir (which closes the JarFile) in
org.reflections.Reflections.scan(URL):260
the second one gets the IllegalStateException.

Cheers,

Christian