class StringUtil {

  public static String join(String[] array, String separator) {
    int len = array.length;
    if (len == 0) {
      return "";
    }

    StringBuilder out = new StringBuilder();
    out.append(array[0]);
    for (int i = 1; i < len; i++) {
      out.append(separator).append(array[i]);
    }
    return out.toString();
  }

}