* map.
   */
  final class WriteThroughEntry extends SimpleEntry<K, V> {
    WriteThroughEntry(K key, V value) {
      super(key, value);
    }

    /*
     * We inherit equals() and hashCode() instead of overriding them to use keyEquivalence and
     * valueEquivalence.
     */

    @Override
    public V setValue(V newValue) {
      put(getKey(), newValue);