Short way to convert a string or character to a new one in java

Question

I am trying to convert characters in a string into a new character. Essentially it would convert ATCG into TAGC. Is there a shorter way of doing this than writing a for loop and checking each character such as the tr command in bash?

Give a minimal verifiable example of what you're doing so we can help you. Read this https://stackoverflow.com/help/asking — Victor M Perez, Jan 09 '18 at 16:17
You'd have to have a `Map` declaring keys and values. Then loop or stream the characters, do the conversion, and collect to String. For people unclear what `tr` is, see: https://en.wikipedia.org/wiki/Tr_(Unix) — ifly6, Jan 09 '18 at 16:18
@ElliottFrisch seems like base paring in DNA. In short: yes. Substitute all `'A'`'s with `'T'`'s (and vice-versa) and all `'C'`'s with `'G'`'s (and vice-versa). [idownvotedbecau.se/noresearch/](http://idownvotedbecau.se/noresearch/) — Turing85, Jan 09 '18 at 16:20
@Turing85 I considered that, it could also be swap each adjacent pair of characters (in this example). — Elliott Frisch, Jan 09 '18 at 17:16

score 0 · Answer 1 · answered Jan 09 '18 at 20:30

@ifly6's comment already sketched the way to go:

A Map defines the conversion rules for single characters.
The String transformation is done by streaming the characters, doing the conversion for each character (using the Map), and collecting them to a String.

public class Main {

    private static Map<Character, Character> charMap = new HashMap<>();

    static {
        charMap.put('A', 'T');
        charMap.put('T', 'A');
        charMap.put('C', 'G');
        charMap.put('G', 'C');
    }

    public static String transform(String s) {
        return s.chars()                               // IntStream
                .mapToObj(c -> charMap.get((char) c))  // Stream<Character>
                .map(Object::toString)                 // Stream<String>
                .collect(Collectors.joining());        // String
    }

    public static void main(String[] args) {
        System.out.println(transform("ATTCGAGC"));     // prints "TAAGCTCG"
    }
}

You will notice that (at least for newbies) streams are much harder to understand than conventional for loops.

I recommend to read about Java 8 streams and the Javadocs of the methods used in the code above.

Short way to convert a string or character to a new one in java

1 Answers1