}

  private final String separator;

  private Joiner(String separator) {
    this.separator = checkNotNull(separator);
  }

  private Joiner(Joiner prototype) {
    this.separator = prototype.separator;
  }

  /*
   * In this file, we use <? extends @Nullable Object> instead of <?> to work around a Kotlin bug

  }

  private final String separator;

  private Joiner(String separator) {
    this.separator = checkNotNull(separator);
  }

  private Joiner(Joiner prototype) {
    this.separator = prototype.separator;
  }

  /*
   * In this file, we use <? extends @Nullable Object> instead of <?> to work around a Kotlin bug