From the fact that it is. You do not repackage foreign classes in your own JAR. JARs are made too be reused themselves, not their contents. If one JAR wants to use another one, that is what the classpath is for. There is also no standard JDK tool which you give 5 JARs that makes you one fat JAR out of it. Also Jigsaw is a clear sign that this is not the intended usage, because the whole Jigsaw does not work if you repackage JAR contents and so on.