code: public static <T> T[] concat(T[] array, @Nullable T element) {
      T[] result = Arrays.copyOf(array, array.length + 1);
      result[array.length] = element;
      return result;
    }
docs: Returns a new array that appends {@code element} to {@code array}.
  
  @param array the array of elements to prepend
  @param element the element to append to the end
  @return an array whose size is one larger than {@code array}, with the same contents as {@code
  array}, plus {@code element} occupying the last position.