An attempt to call com.google.common.reflect.ClassPath#from ends with NullPointerException on IBM WebSphere 8.5.5.5. The following snippet from com.google.common.reflect.ClassPath#getClassPathEntries causes issues:

URLClassLoader urlClassLoader = (URLClassLoader) classloader;
for (URL entry : urlClassLoader.getURLs()) {

getURLs() on com.ibm.ws.bootstrap.ExtClassLoader returns null:

    public URL[] getURLs() {
        return null;
    }

    public URL[] _getURLs() {
        return super.getURLs();
    }

It looks like IBM made this on purpose, so I guess reporting to Guava is more appropriate here.