private ClassDoc[] getArray(Map<String, Set<ClassDoc>> m, String key) {
   Set<ClassDoc> s = m.get(key);
   if (s == null) {
     return new ClassDoc[] {};
   } else {
     return s.toArray(new ClassDoc[] {});
   }
 }
 /** Return the array of package names that this catalog stores ClassDocs for. */
 public String[] packageNames() {
   return packageSet.toArray(new String[] {});
 }