For example, take this piece of code:

   for(String line : Files.readAllLines(inputFile.toPath(),
           Charset.defaultCharset())) {
   }

Select "Charset.defaultCharset()", and hit alt-shift-V ["Introduce Variable"].

Delete the default name, and enter the new name "charSet". Notice that as you enter it, once you hit "char", the OK button is greyed out, and a warning pops up that this isn't a valid name. As you keep typing, the warning goes away, but the "OK" button is never un-greyed.