static Set<String> getLegacyPackages() {
        ResourceBundle legacyBundle
            = ResourceBundle.getBundle("com.sun.tools.javac.resources.legacy");
        Set<String> keys = new HashSet<String>();
        for (Enumeration<String> e = legacyBundle.getKeys(); e.hasMoreElements(); )
            keys.add(e.nextElement());
        return keys;
    }