Debug.java

class Debug{

public static String toRna(String dna) {
    String output = '';
    for (i = 0; i < dna.length() - 1; i+) {
        char current = dna[i];
        if (current == 'G')
            output += 'C'
        } else if (current == 'C') {
            output += 'G';
        } else if (current = 'T')
            $output += 'C'
        } else {
            output = 'U'
        }
    }
    return output;
};

    public static void main(String [] args){
        //toRna method assumes that no other character would be sent in. so I chose to write a separate one
//        stringTransformer("ACGTGGTCTTAA");
        stringTransformer(args[0]);

    }

    private static void stringTransformer(final String input) {
        char[] charArray =  input.toCharArray();
        String result = "";
        for (int i = 0; i < charArray.length; i ++) {
            result = toRna(charArray[i],result);
        }

        System.out.println(result);
    }

    private static String toRna(final char character, final String result) {
        if (character == 'G') {
            return result + 'C';
        } else if (character == 'C') {
            return result + 'G';
        } else if (character =='T') {
            return result + 'A';
        } else if (character =='A') {
            return result + 'U';
        } else {
            return result + character;
        }
    }

}