public class Exercice1_2 {

  /**
   * Ce programme doit me retourner le complément d'une chaîne d'ADN mais ça ne fonctionne pas.
   */
  public static void main(String[] args) {
    System.out.println(makeDNAComplement("AATGCCGGC"));
    System.out.println(makeDNAComplement("TTACGGCCG"));
    System.out.println(makeDNAComplement("AATTCCGTACGGA"));
  }

  /**
   * Function that returns a DNA string complement.
   * 
   * @param dna the DNA string to complement.
   * @return complemented DNA string. Example : input ("AATGCCGGC") => output ("TTACGGCCG").
   */
  public static String makeDNAComplement(String dna) {
    String result = "";
    if (dna != null && !dna.isEmpty()) {
      char[] dnaCharArray = dna.toCharArray();

      for (char dnaChar : dnaCharArray) {
        switch (dnaChar) {
        case 'A':
          result = result.concat("T");
        case 'T':
          result = result.concat("A");
        case 'C':
          result = result.concat("G");
        case 'G':
          result = result.concat("C");
        }
      }
    }
    return result;
  }

}