Set<RefPackage> ( RefPackage refPackage) { final Set<RefPackage> dependents = refPackage.getUserData(TRANSITIVE_DEPENDENT_PACKAGES_KEY); if (dependents != null) { return dependents; } final Set<RefPackage> newDependents = new HashSet<>(); tabulateTransitiveDependentPackages(refPackage, newDependents); refPackage.putUserData(TRANSITIVE_DEPENDENT_PACKAGES_KEY, newDependents); return newDependents; }