*     remaining configuration and cache building
   * @return this {@code CacheBuilder} instance (for chaining)
   * @throws IllegalStateException if a removal listener was already set
   */
  public <K1 extends K, V1 extends V> CacheBuilder<K1, V1> removalListener(
      RemovalListener<? super K1, ? super V1> listener) {
    checkState(this.removalListener == null);

   *     remaining configuration and cache building
   * @return this {@code CacheBuilder} instance (for chaining)
   * @throws IllegalStateException if a removal listener was already set
   */
  public <K1 extends K, V1 extends V> CacheBuilder<K1, V1> removalListener(
      RemovalListener<? super K1, ? super V1> listener) {
    checkState(this.removalListener == null);