code: public static String concatStrings(final String delimiter, final String... texts) {
          final String delim = delimiter == null ? "" : delimiter;
          final StringBuilder conCatStrBldr = new StringBuilder();
          if (null != texts) {
              for (final String text : texts) {
                  conCatStrBldr.append(delim);
                  conCatStrBldr.append(text);
              }
          }
          final String conCatedStr = conCatStrBldr.toString();
          return delim.length() > 0 && conCatedStr.startsWith(delim) ? conCatedStr.substring(1) : conCatedStr;
      }
docs: Concatenate the given text all the string arguments with the given
  delimiter.
  
  @param delimiter
  the delimiter text to be used while concatenation.
  @param texts
  all these string values will be concatenated with the given
  delimiter.
  @return null in case no text arguments to be compared. just concatenation
  of all texts arguments if "delimiter" is null or empty.
  concatenation of all texts arguments with "delimiter" if it not
  null.