# [Java (JDK)], 71 bytes <!-- language-all: lang-java --> (b,B)->{B="_";for(b=47;b++<122;)if(b<58|b>64&&b<91|b>96)B+=b;return B;} [Try it online!][TIO-l01p4s8z] [Java (JDK)]: http://jdk.java.net/ [TIO-l01p4s8z]: https://tio.run/##NU5Na8IwGL77K1560ITWgOJ0kraHCLvt5HGMkdTGpca0JG8Ecf3tXca20/PA89nJm1x2p8vUWBkCvErj4DEDGKKypoGAEhPcenOCa9LIEb1x57d3kP4caLJ2qYBFNJbp6Bo0vWPCvPzR8vApvWyw9QX8Jv@xBl1NRBWCLuuHqLKPjOveE1Vtdlzleblarzk1mqjy6flL1dvNfK7K/SrR/ZaKvFLctxi9A8HHiafDAMd7wPbK@ohsSBNoHdFMDoO9kwUsCsgySn@c42ycvgE "Java (JDK) – Try It Online" Inspired by an answer from dorukayhan this is a ```java.util.function.BiFunction<Character, String, String>```