wsl/window terminal: Java 14 switch expressions unrecognized

problem¶

build succeeds in IDEA, but automated build fails

$ ./gradlew

> Task :compileJava FAILED
Wordle/src/game/ui/WordleFrame.java:60: error: illegal start of expression
    var background = switch (tallyResultOfOneLetter) {
                     ^
Wordle/src/game/ui/WordleFrame.java:61: error: : expected
      case EXACT -> COLOR_OF_EXACT;
                                  ^
Wordle/src/game/ui/WordleFrame.java:62: error: : expected
      case MATCH -> COLOR_OF_MATCH;
                                  ^
Wordle/src/game/ui/WordleFrame.java:63: error: : expected
      case NO_MATCH -> COLOR_OF_NO_MATCH;
                                        ^
4 errors

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileJava'.
> Compilation failed; see the compiler error output for details.

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 1s
2 actionable tasks: 2 executed

solution¶

Later, it was found that the java JDK used in IDEA is 17, while the automated build in wsl uses JDK 11, which has not reached JDK14, so the expression of 14 cannot be recognized.

Then upgrade the JDK in wsl.

Upgrade to Java 17 here.

Specific operation process: Ubuntu 20 under wsl2

first enter

sudo apt update

Specific upgrade process:

Step 1:

sudo add-apt-repository ppa:linuxuprising/java

Step 2:

sudo apt-get update
sudo apt-get install oracle-java17-installer oracle-java17-set-default

The terms that appear, swipe the pagedown key to the bottom, and use the up, down, left and right keys to select the ok below

Then press the arrow keys to select yes, press Enter

Then the download starts

After installation is complete:

$ java --version

java 17.0.1 2021-10-19 LTS
Java(TM) SE Runtime Environment (build 17.0.1+12-LTS-39)
Java HotSpot(TM) 64-Bit Server VM (build 17.0.1+12-LTS-39, mixed mode, sharing)