code: public StrBuilder appendWithSeparators(final Object[] array, final String separator) {
          if (array != null && array.length > 0) {
              final String sep = Objects.toString(separator, "");
              append(array[0]);
              for (int i = 1; i < array.length; i++) {
                  append(sep);
                  append(array[i]);
              }
          }
          return this;
      }
docs: Appends an array placing separators between each value, but
  not before the first or after the last.
  Appending a null array will have no effect.
  Each object is appended using {@link #append(Object)}.
  
  @param array  the array to append
  @param separator  the separator to use, null means no separator
  @return this, to enable chaining