code: public WebhookMessage build()
      {
          if (isEmpty())
              throw new IllegalStateException("Cannot build an empty message!");
          return new WebhookMessage(username, avatarUrl, content.toString(), embeds, isTTS, fileIndex == 0 ? null : Arrays.copyOf(files, fileIndex));
      }
docs: Builds a {@link net.dv8tion.jda.webhook.WebhookMessage WebhookMessage} instance
  with the current state of this builder.
  
  @throws java.lang.IllegalStateException
  If this builder is empty
  
  @return The resulting {@link net.dv8tion.jda.webhook.WebhookMessage WebhookMessage}