CaselessUnmodifiableMultivaluedMap extends CaselessMultivaluedMap<T> { @Override public Set<String> keySet() { if (keys == null) { keys = new ReadOnlyKeySet(); } return keys; } CaselessUnmodifiableMultivaluedMap();  CaselessUnmodifiableMultivaluedMap(int capacity);  CaselessUnmodifiableMultivaluedMap(Map<String, List<T>> m); @Override void add(String key, T value); @Override void clear(); @Override Set<Entry<String, List<T>>> entrySet(); @Override List<T> get(Object key); @Override List<T> getList(String key); @Override Set<String> keySet(); @Override List<T> put(String key, List<T> value); @Override void putAll(Map<? extends String, ? extends List<T>> m); @Override void putSingle(String key, T value); @Override List<T> remove(Object key); @Override void addAll(String key, T... newValues); @Override void addAll(String key, List<T> valueList); @Override void addFirst(String key, T value); @Override Collection<List<T>> values();  }
@Test(expected = UnsupportedOperationException.class) public void testKeysRemoveAll() { map.keySet().removeAll(Arrays.asList("k", "y", "e")); }
@Test(expected = UnsupportedOperationException.class) public void testKeysRetainAll() { map.keySet().retainAll(Arrays.asList("k", "y")); }