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Java Introduction to Functional Programming Reduction and Aggregation Using a Range to Produce a Menu

Posted by Devin Rayner
Devin Rayner
14,650 Points

How to produce a menu using the range function?

I have been working on this problem for quite some time and I just can't figure it out?

1 Answer

Michael Switzer
Michael Switzer
7,490 Points
Michael Switzer
Michael Switzer
7,490 Points

This was a real struggle for me too. Here is what I finally ended up with:

  public static List<String> getStateCodesFromRecords(List<HousingRecord> records) {
    return records.stream()
      // TODO: Map the stream to the state code
      .map(HousingRecord::getState)
      // TODO: Filter out any records without a state
      .filter(state -> !state.isEmpty())
      // TODO: There are duplicate state codes in the records, make sure we have a unique representation
      .distinct()
      // TODO: Sort them alphabetically
      .sorted()
      // TODO: Collect them into a new list.
      .collect(Collectors.toList());
  }

  public static void displayStateCodeMenuDeclaratively(List<String> stateCodes) {
    // TODO: Use a range to display a numbered list of the states, starting at 1.
    IntStream.rangeClosed(1, stateCodes.size())
      .mapToObj(count -> String.format("%d. %s", count, stateCodes.get(count - 1)))
      .forEach(System.out::println);
  }