public PackagePathCache(
     ImmutableSet<IjFolder> startingFolders, JavaPackageFinder javaPackageFinder) {
   delegate = new ParsingJavaPackageFinder.PackagePathCache();
   for (IjFolder startingFolder : startingFolders) {
     if (!startingFolder.getWantsPackagePrefix()) {
       continue;
     }
     Path path =
         FluentIterable.from(startingFolder.getInputs()).first().or(lookupPath(startingFolder));
     delegate.insert(path, javaPackageFinder.findJavaPackageFolder(path));
   }
 }
 public Optional<Path> lookup(IjFolder folder) {
   return delegate.lookup(lookupPath(folder));
 }