This week's book giveaway is in the General Computing forum. We're giving away four copies of Arduino in Action and have Martin Evans, Joshua Noble, and Jordan Hochenbaum on-line! See this thread for details.
"its a new string" is a String, not a StringBuffer. As such, it can't be assigned to a StringBuffer. String literals only work as Strings, not for any other classes.
" new StringBuffer("its a new string buffer") " converts a String to a StringBuffer, so it can be assigned to one.