Sometimes one doesn't want to expose the full scope of file URLs given to https://github.com/codehaus-plexus/plexus-classworlds/blob/1862fc6b1bfe1c0b924bcca07dfcc08b9025562b/src/main/java/org/codehaus/plexus/classworlds/realm/ClassRealm.java#L210 but only some classes. A concrete use case are Maven extensions loaded from regular Maven plugins (https://issues.apache.org/jira/browse/MNG-7574).