static L<File> deletableProgramJars() {
  Set<S> names = asHashSet(map fileName(programJarsLoadedInAllVMs()));
  ret [File f : filesInDirs(javaxCachesDir(#1002203), javaxCachesDir(#1001638))
    | hasExtension(f, ".jar") && !names.contains(fileName(f))];
}