question: public static String normalizeDigits ( String token ) { StringBuilder sb = new StringBuilder ( token . length ( ) ) ; int len = token . length ( ) ; for ( int i = 0 ; i < len ; ++ i ) { char c = token . charAt ( i ) ; sb . append ( Character . isDigit ( c ) ? "0" : c ) ; } return sb . toString ( ) ; }
target:  Map all characters in the range [0-9] to 0 in the input string.