docs: public static <T> T[] append(T[] array1, T[] array2) {
          T[] dst = (T[]) Array.newInstance(array1.getClass().getComponentType(), array1.length + array2.length);
          System.arraycopy(array1, 0, dst, 0, array1.length);
          System.arraycopy(array2, 0, dst, array1.length, array2.length);
          return dst;
      }