Enthuware

The question says
Which of these are not part of the StringBuilder class?

You mark as correct

setLength(int)

that IS part of the StringBuilder class. I think there's an error in this question!

I see that it is marked as incorrect.

HTH,
Paul.

What exactly we should know about StringBuilder class? I've never seen and/or used setLength method, for example.

See this thread: viewtopic.php?f=2&t=1213&p=2634

Hi, There are 2 correct answers trim() and setLengght(), but only one is marked as correct.
Am I missing something?

No, there is only one correct option i.e. option 1.
Please read the question carefully. It says "NOT part of".

Not sure where is the setLength method description copied from, but it describes string buffer, while the question is not about StringBuffer?
Javadoc of setLenght in AbstractStringBuilder doesn't mention neither string builder not buffer.

Sets the length of the character sequence.

Both StringBuilder and StringBuffer are based on an internal "buffer" of characters or character sequence. The description is applicable to both.

This looks like Javadoc, maybe the old one. Wouldn't it be better to include the new one in the question? Also it is technically not StringBuffer, so if you want to keep it and you say there are based on string buffer, shouldn't it say "underlying buffer" rather than "this string buffer"? This sentence just sounds like this StringBuilder is somehow a buffer.

Yes, I agree.