code: public Object opt(int index) {
  		return (index < 0 || index >= this.length()) ? null : this.list
  				.get(index);
  	}
docs: Get the optional object value associated with an index.
  
  @param index The index must be between 0 and length() - 1.
  @return An object value, or null if there is no object at that index.