How to do some operation when Optional has null value?

Question

In my stream I want to get MainMenuOption based on user's input. If enum MainMenuOptions contains such option I want to return it, if not - print some message "THERE IS NO SUCH OPTION" and get user's input again.

return Arrays.stream(MainMenuOptions.values())
            .filter(x -> x.getCommand().equals(ConsoleInput.getNextLineFromUser()))
            .findFirst() // it returns Optional<MainMenuOptions>
            .orElse(); //or Else return some value, cannot do something

How I can achive it with Java Steams?

Thank you in advance.

A thought, return the Optional<MainMenuOptions> and leave to the caller to print any message. The caller may for example use ifPresentOrElse() (since Java 9). — Anonymous
– Anonymous, Commented Jun 17, 2020 at 18:37
You can throw custom exception and ask user to select again if it raise orElseThrow(()->new MenuOptionNotFoundException()) — Alex
– Alex, Commented Jun 17, 2020 at 18:44

Eklavya · Accepted Answer · 2020-06-17 18:50:40Z

5

Use a Optional.map operation before orElse to transform to Optional<String> such as

return Arrays.stream(MainMenuOptions.values())
        .filter(x -> x.getCommand().equals(ConsoleInput.getNextLineFromUser()))
        .findFirst()
        .map(MainMenuOptions::name)
        .orElse("THERE IS NO SUCH OPTION");

edited Jun 17, 2020 at 18:50

Eklavya

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answered Jun 17, 2020 at 18:38

Naman

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1 Comment

MrFisherman Over a year ago

Thank you for help.

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