code: @SuppressWarnings({"unchecked"})
      public static <T> T[] arrayOf(T[] firstElements, T lastElement) {
          checkArgNotNull(firstElements, "firstElements");
          Class elementType = firstElements.getClass().getComponentType();
          T[] array = (T[]) Array.newInstance(elementType, firstElements.length + 1);
          System.arraycopy(firstElements, 0, array, 0, firstElements.length);
          array[firstElements.length] = lastElement;
          return array;
      }
docs: Joins the given arguments into one array.
  
  @param firstElements the first elements
  @param lastElement   the element to append
  @return a new array containing all arguments.