環境

IntelliJ IDEA 2019.2.4 (Community Edition)

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New ProjectでProject SDKに13を選択する。

https://twitter.com/java/status/1193898422849269760 の http://blog.codefx.org/java/switch-expressions/ を参考にサンプルコードを書く。

import java.io.FileNotFoundException;

public class Main {

    static enum MY_BOOLEAN {
        TRUE, FALSE, FILE_NOT_FOUND,
    }

    public static void main(String[] args) throws Exception {
        MY_BOOLEAN ternaryBool = MY_BOOLEAN.TRUE;

        boolean result = switch (ternaryBool) {
            case TRUE -> true;
            case FALSE -> false;
            case FILE_NOT_FOUND -> throw new RuntimeException("This is ridiculous!", new FileNotFoundException());
            // as we'll see in "Exhaustiveness", `default` is not necessary
            default -> throw new IllegalArgumentException("Seriously?! 🤬");
        };
        System.out.println(result);

    }
}

実行すると下記のようなエラーになる。

Information:java: Errors occurred while compiling module 'untitled'
Information:javac 13.0.1 was used to compile java sources
Information:2019/11/15 16:13 - Build completed with 1 error and 0 warnings in 3 s 286 ms
Error:java: invalid source release 12 with --enable-preview
  (preview language features are only supported for release 13)

Open Module Settings -> Project Settings -> Modules -> Language level を13 (Preview)に変更する。

これで動く。language levelを変えてあげれば--enable-previewは無くても動くらしい。

IntelliJ IDEAでjava 13のswitchをためす

環境

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