}
    }
    cachingHashMap.clear();
  }

  @Override
  public V putIfAbsent(K key, V value) {
    V currentValue = get(key);
    if (currentValue != null) {
      return currentValue;
    }
    return put(key, value);
  }

  @CanIgnoreReturnValue
  @Override
  public boolean remove(Object key, Object value) {
    if (value.equals(get(key))) {

      local = Optional.absent();
      for (String currentValue : parameters.get(CHARSET_ATTRIBUTE)) {
        if (value == null) {
          value = currentValue;
          local = Optional.of(Charset.forName(value));
        } else if (!value.equals(currentValue)) {
          throw new IllegalStateException(
              "Multiple charset values defined: " + value + ", " + currentValue);
        }
      }
      parsedCharset = local;

      local = Optional.absent();
      for (String currentValue : parameters.get(CHARSET_ATTRIBUTE)) {
        if (value == null) {
          value = currentValue;
          local = Optional.of(Charset.forName(value));
        } else if (!value.equals(currentValue)) {
          throw new IllegalStateException(
              "Multiple charset values defined: " + value + ", " + currentValue);
        }
      }
      parsedCharset = local;