code: public MessageBuilder setContent(String content)
      {
          if (content == null)
          {
              builder.setLength(0);
          }
          else
          {
              Checks.check(content.length() <= Message.MAX_CONTENT_LENGTH, "Content length may not exceed %d!", Message.MAX_CONTENT_LENGTH);
              final int newLength = Math.max(builder.length(), content.length());
              builder.replace(0, newLength, content);
          }
          return this;
      }
docs: Sets the content of the resulting Message
  <br>This will replace already added content.
  
  @param  content
  The content to use, or {@code null} to reset the content
  
  @throws java.lang.IllegalArgumentException
  If the provided content exceeds {@link net.dv8tion.jda.core.entities.Message#MAX_CONTENT_LENGTH Message.MAX_CONTENT_LENGTH}
  
  @return The MessageBuilder instance. Useful for chaining.
  
  @see    net.dv8tion.jda.core.entities.Message#getContentRaw()