question: public static String quote ( String s ) { StringBuilder buf = new StringBuilder ( ) ; for ( int i = 0 ; i < s . length ( ) ; i ++ ) { buf . append ( quote ( s . charAt ( i ) ) ) ; } return buf . toString ( ) ; }
target:  Escapes each character in a string that has an escape sequence or is non-printable ASCII.  Leaves non-ASCII characters alone.