* String a3 = peekingIterator.next(); // also returns "a"
   * }</pre>
   *
   * <p>Any structural changes to the underlying iteration (aside from those performed by the
   * iterator's own {@link PeekingIterator#remove()} method) will leave the iterator in an undefined
   * state.
   *
   * <p>The returned iterator does not support removal after peeking, as explained by {@link
   * PeekingIterator#remove()}.