Font.getAdvance()
You cannot total the advances from Font.getAdvance(char c) to get the advance for a String. I'm not sure why, but totaling the values returned by Font.getAdvance(char c) does not necessarily give you the same total as calling Font.getAdvance(String str) on a String containing those same characters. The string "book may be reproduced or" is an example of this. I confirmed it using the BBClarity font, size 18.