code: public Object peek(int n) throws EmptyStackException {
          int m = (size() - n) - 1;
          if (m < 0) {
              throw new EmptyStackException();
          }
          return get(m);
      }
docs: Returns the n'th item down (zero-relative) from the top of this
  stack without removing it.
  
  @param n the number of items down to go
  @return the n'th item on the stack, zero relative
  @throws EmptyStackException if there are not enough items on the
  stack to satisfy this request