test against JDK21 (LTS)

.github/workflows/ci.yml

@@ -11,6 +11,8 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: olafurpg/setup-scala@v14
+        with:
+          java-version: 8
       - run: sbt test scripted
   jdk11:
     name: JDK11 tests
@@ -19,7 +21,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: olafurpg/setup-scala@v14
         with:
-          java-version: adopt@1.11
+          java-version: 11
       - run: sbt test scripted
   jdk17:
     name: JDK17 tests
@@ -30,6 +32,15 @@ jobs:
         with:
           java-version: 17
       - run: sbt "test; scripted sbt-scalafix/*"
+  jdk21:
+    name: JDK21 tests
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: olafurpg/setup-scala@v14
+        with:
+          java-version: 21
+      - run: sbt "test; scripted sbt-scalafix/*"
   windows:
     name: Windows tests
     runs-on: windows-latest

build.sbt

@@ -51,10 +51,14 @@ scalaVersion := "2.12.19"
 pluginCrossBuild / sbtVersion := "1.3.1"
 
 scriptedSbt := {
-  if (System.getProperty("java.specification.version").toDouble < 17)
-    "1.3.0"
-  else
+  val jdk = System.getProperty("java.specification.version").toDouble
+
+  if (jdk >= 21)
+    "1.9.0" // first release that supports JDK21
+  else if (jdk >= 17)
     "1.5.5" // first release that supports JDK17
+  else
+    "1.3.0"
 }
 
 libraryDependencies += compilerPlugin(scalafixSemanticdb)