public String arrayToString(String[] array) {
//    if (array == null) return null;
    return Arrays.toString(array);
}

public String[] stringToArray(String arrayString) {
    if (arrayString == null) return null;
    String[] array;
    if (arrayString.startsWith("[") && arrayString.endsWith("]"))
     array = arrayString.substring(1, arrayString.length()-1).split(",");
    else
     array = arrayString.split(","); 
    return array;
}

  public static String[] getUniqueElements(String[] old_array, String[] new_array) {
    if (new_array == null || new_array.length == 0) return new String[0];
    if (old_array == null || old_array.length == 0) return new_array;
    List<String> unique = new ArrayList<String>();
    for (String n : new_array) {
      boolean contain = false;
      for (String o : old_array) {
        if (n.equals(o)) contain = true;
      }
      if (!contain)
        unique.add(n);
    }
    return unique.toArray(new String[unique.size()]);
  }