docs: public static <T> T[] concatenate(final T[] first, final T[]... rest) {
          int totalLength = first.length;
  
          for (final T[] array : rest) {
              totalLength += array.length;
          }
  
          final T[] ret = Arrays.copyOf(first, totalLength);
          int offset = first.length;
  
          for (final T[] array : rest) {
              System.arraycopy(array, 0, ret, offset, array.length);
              offset += array.length;
          }
  
          return ret;
      }