Test using Java 21

.github/workflows/main.yml

@@ -5,7 +5,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        java-version: [ 8, 11, 17, 18 ]
+        java-version: [ 8, 11, 17, 21 ]
     steps:
       - uses: actions/checkout@0ad4b8fadaa221de15dcec353f45205ec38ea70b # v4
 
@@ -19,3 +19,5 @@ jobs:
         if: ${{ matrix.java-version == 8 }}
 
       - run: ./gradlew assemble check --info
+        env:
+          JAVA_TOOLCHAIN: ${{ matrix.java-version }}

build.gradle

@@ -2,15 +2,31 @@ plugins {
     id 'java'
     id 'signing'
     id 'maven-publish'
-    id "com.diffplug.spotless" version "6.13.0"
+    id "com.diffplug.spotless" version "6.25.0"
 }
 
-compileJava {
-    if (JavaVersion.current().ordinal() > JavaVersion.VERSION_1_8.ordinal()) {
-        options.compilerArgs.addAll(['--release', '8'])
+var javaToolchain = System.getenv('JAVA_TOOLCHAIN')
+
+java {
+    if (javaToolchain != null) {
+        toolchain {
+            languageVersion = JavaLanguageVersion.of(javaToolchain)
+        }
     }
 }
 
+compileJava {
+    sourceCompatibility = '8'
+    targetCompatibility = '8'
+    options.compilerArgs.add('-Xlint')
+}
+
+compileTestJava {
+    sourceCompatibility = '8'
+    targetCompatibility = '8'
+    options.compilerArgs.add('-Xlint')
+}
+
 repositories {
     mavenLocal()
     mavenCentral()
@@ -22,7 +38,8 @@ dependencies {
 
 spotless {
     java {
-        palantirJavaFormat()
+        // remove when spotless moved to this Palantir version
+        palantirJavaFormat("2.38.0")
     }
 }