!7

p {
  L l = ll();
  assertSame("ArrayList", collectionMutex(l), l);
  
  // not so trivial
  // new HashMap map;
  // assertSame("HashMap", collectionMutex(keySet(map)), map);
  
  Map map = caseInsensitiveMap();
  assertSame("keySet/caseInsensitiveMap", collectionMutex(printClassName(keySet(map))), map);
  assertSame("navigableKeys/caseInsensitiveMap", collectionMutex(printClassName(navigableKeys(map))), map);
  
  map.put("bla", "");
  assertSame("prefixSubSet/navigableKeys/caseInsensitiveMap", collectionMutex(printClassName(prefixSubSet(navigableKeys(map), "bla"))), map);
  
  print("OK (excluding HashMap)");
}