The ZipFileIndexFileObject class from ZipFileIndexArchive.java implements a
content cache using a HashMap. The cache stores contents of files - java or
class files - indexed by the name of the class. By "name" we mean only the
class name and not the fully-qualified name (that would include the package
name). If a certain zip/jar archive contains two classes with the same name,
in different packages, a key collision occurs. The hashCode() and equals()
method for the ZipFileIndexFileObject class fail to distinguish between two
such keys, leading to a wrong value (file content) being retrieved. This
happens only if the "last modified" timestamps for the two files are equal.

This can lead to various problems. For example, a unexpected compilation
failure problem with wsgen (wsgen uses apt, apt uses javac).