'existing' | 'Concat'   | String::concat                              | 'existingValueConcat'
        'existing' | ''         | AccessTrackingPropertiesTest::removeMapping | null
        'missing'  | 'newValue' | String::concat                              | 'newValue'
    }

    return value != null && value.equals(get(rowKey, columnKey));
  }

  /** Remove a row key / column key / value mapping, if present. */
  private boolean removeMapping(
      @CheckForNull Object rowKey, @CheckForNull Object columnKey, @CheckForNull Object value) {
    if (containsMapping(rowKey, columnKey, value)) {
      remove(rowKey, columnKey);
      return true;
    }

    return value != null && value.equals(get(rowKey, columnKey));
  }

  /** Remove a row key / column key / value mapping, if present. */
  private boolean removeMapping(
      @CheckForNull Object rowKey, @CheckForNull Object columnKey, @CheckForNull Object value) {
    if (containsMapping(rowKey, columnKey, value)) {
      remove(rowKey, columnKey);
      return true;
    }