Update build and test to require Java 21

.github/actions/run-gradle/action.yml

@@ -12,7 +12,7 @@ runs:
       id: setup-gradle-jdk
       with:
         distribution: temurin
-        java-version: 17
+        java-version: 21
     - uses: gradle/gradle-build-action@v2
       env:
         JAVA_HOME: ${{ steps.setup-gradle-jdk.outputs.path }}

.github/workflows/cross-version.yml

@@ -20,7 +20,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        jdk: [21, 22]
+        jdk: [22]
     name: "OpenJDK ${{ matrix.jdk }}"
     runs-on: ubuntu-latest
     steps:

.github/workflows/main.yml

@@ -31,7 +31,7 @@ jobs:
       uses: graalvm/setup-graalvm@v1
       with:
         version: 'latest'
-        java-version: '17'
+        java-version: '21'
         components: 'native-image'
         github-token: ${{ secrets.GITHUB_TOKEN }}
     - name: Build

README.md

@@ -65,7 +65,7 @@ task outputs from previous CI builds.
 
 ## Building from Source
 
-You need [JDK 17] to build JUnit 5. [Gradle toolchains] are used to detect and
+You need [JDK 21] to build JUnit 5. [Gradle toolchains] are used to detect and
 potentially download additional JDKs for compilation and test execution.
 
 All modules can be _built_ and _tested_ with the [Gradle Wrapper] using the following command.
@@ -100,7 +100,7 @@ See also <https://repo1.maven.org/maven2/org/junit/> for releases and
 [Gradle Wrapper]: https://docs.gradle.org/current/userguide/gradle_wrapper.html#sec:using_wrapper
 [JaCoCo]: https://www.eclemma.org/jacoco/
 [Javadoc]: https://junit.org/junit5/docs/current/api/
-[JDK 17]: https://foojay.io/almanac/java-17/
+[JDK 21]: https://foojay.io/almanac/java-21/
 [Release Notes]: https://junit.org/junit5/docs/current/release-notes/
 [Samples]: https://github.com/junit-team/junit5-samples
 [StackOverflow]: https://stackoverflow.com/questions/tagged/junit5

gradle/plugins/common/src/main/kotlin/JavaLibraryExtension.kt

@@ -2,6 +2,6 @@ import org.gradle.api.JavaVersion
 
 open class JavaLibraryExtension {
     var mainJavaVersion: JavaVersion = JavaVersion.VERSION_1_8
-    var testJavaVersion: JavaVersion = JavaVersion.VERSION_17
+    var testJavaVersion: JavaVersion = JavaVersion.VERSION_21
     var configureRelease: Boolean = true
 }

gradle/plugins/common/src/main/kotlin/junitbuild.java-toolchain-conventions.gradle.kts

@@ -5,7 +5,7 @@ plugins {
 }
 
 project.pluginManager.withPlugin("java") {
-	val defaultLanguageVersion = JavaLanguageVersion.of(17)
+	val defaultLanguageVersion = JavaLanguageVersion.of(21)
 	val javaLanguageVersion = buildParameters.javaToolchainVersion.map { JavaLanguageVersion.of(it) }.getOrElse(defaultLanguageVersion)
 
 	val extension = the<JavaPluginExtension>()

gradle/plugins/settings.gradle.kts

@@ -1,4 +1,4 @@
-val expectedJavaVersion = JavaVersion.VERSION_17
+val expectedJavaVersion = JavaVersion.VERSION_21
 val actualJavaVersion = JavaVersion.current()
 require(actualJavaVersion == expectedJavaVersion) {
 	"The JUnit 5 build must be executed with Java ${expectedJavaVersion.majorVersion}. Currently executing with Java ${actualJavaVersion.majorVersion}."

junit-jupiter-params/src/test/java/org/junit/jupiter/params/converter/DefaultArgumentConverterTests.java

@@ -338,6 +338,7 @@ void convertsStringToCurrency() {
 	}
 
 	@Test
+	@SuppressWarnings("deprecation")
 	void convertsStringToLocale() {
 		assertConverts("en", Locale.class, Locale.ENGLISH);
 		assertConverts("en_us", Locale.class, new Locale(Locale.US.toString()));