Java 12 intellij switch expressions doesn't work

Question

I try to use Java 12 in IntelliJ but when I try to run My app occurs error

Error:(57, 32) java: switch expressions are a preview feature and are disabled by default.
  (use --enable-preview to enable switch expressions)

I added in app configuration VM option --enable-preview but this error still occurs. I added SDK paths. Anyone have idea what I do wrong?

List<Car> sortedCars = switch (sortType) {
    case COLOR -> cars.stream().sorted(Comparator.comparing(Car::getColor)).collect(Collectors.toList());
    case MILEAGE -> cars.stream().sorted(Comparator.comparing(Car::getMileage)).collect(Collectors.toList());
    case MODEL -> cars.stream().sorted(Comparator.comparing(Car::getModel)).collect(Collectors.toList());
    case PRICE -> cars.stream().sorted(Comparator.comparing(Car::getPrice)).collect(Collectors.toList());
};

As a side note, try to avoid code duplication, as otherwise, you are ignoring the actual benefit of switch expressions. Consider `List sortedCars = cars.stream().sorted( switch (sortType) { case COLOR -> Comparator.comparing(Car::getColor); case MILEAGE -> Comparator.comparing(Car::getMileage); case MODEL -> Comparator.comparing(Car::getModel); case PRICE -> Comparator.comparing(Car::getPrice); } ).collect(Collectors.toList());` — Holger, Apr 29 '19 at 13:07
Avoid duplication even further: `List sortedCars = cars.stream().sorted(Comparator.comparing(switch (sortType) { case COLOR -> Car::getColor; case MILEAGE -> Car::getMileage; case MODEL -> Car::getModel; case PRICE -> Car::getPrice; } ).collect(Collectors.toList());` — Advicer, Nov 27 '19 at 10:31

score 6 · Answer 1 · answered May 04 '19 at 15:09

6

By default the Language Level is set to "12 - No new language feature". You need to change it to "12 (Preview) - Switch Expression" and you will get a popup to accept the Preview changes. Post which you will be able to run switch expressions in intellij.

Language Levels Settings

I am using IntelliJ IDEA 2019.1.1 (Community Edition)

answered May 04 '19 at 15:09

Sachin

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When you run from Intellij do you see `--enable-preview` appended in the terminal? Can you share your execution logs or screenshot ? – Sachin May 04 '19 at 17:07
did you figure it out? – Tobiq May 17 '20 at 20:34

score 4 · Answer 2 · answered Apr 28 '19 at 10:27

Please make sure that the "Project language level" setting in the Project Structure dialog for your project is set to Java 12. In this case, IntelliJ IDEA will add the --enable-preview option automatically.

The VM options field in the run configuration affects how your application is launched, not how it's compiled, so adding that option there has no effect.

Java 12 intellij switch expressions doesn't work

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