Update the project to use JDK 21

Upgraded all configurations from JDK 17 to JDK 21. This includes
workflow setups, build gradle files, and compiler settings to ensure
compatibility with the latest Java version.

.github/workflows/main.yml

@@ -10,23 +10,23 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - name: Set up JDK 17
+      - name: Set up JDK 21
         uses: actions/setup-java@v4
         with:
           distribution: temurin
-          java-version: 17
+          java-version: 21
       - name: Run Spotless
         run: ./gradlew spotlessCheck
 
   build:
     runs-on: macos-14
     steps:
       - uses: actions/checkout@v4
-      - name: Set up JDK 17
+      - name: Set up JDK 21
         uses: actions/setup-java@v4
         with:
           distribution: temurin
-          java-version: 17
+          java-version: 21
       - name: Setup Android problem matchers
         uses: jonasb/android-problem-matchers-action@v1
       - name: Build with Gradle

customtabs-example/build.gradle.kts

@@ -26,6 +26,8 @@ dependencies {
     implementation("com.google.android.material:material:1.12.0")
 }
 
+java.toolchain.languageVersion.set(JavaLanguageVersion.of(21))
+
 android {
     namespace = "com.example.saschpe.customtabs"
 
@@ -56,11 +58,4 @@ android {
             signingConfig = signingConfigs.getByName("debug")
         }
     }
-
-    compileOptions {
-        sourceCompatibility = JavaVersion.VERSION_17
-        targetCompatibility = JavaVersion.VERSION_17
-    }
-
-    kotlinOptions.jvmTarget = "17"
 }

customtabs/build.gradle.kts

@@ -32,6 +32,8 @@ dependencies {
     testImplementation("org.mockito:mockito-core:5.13.0")
 }
 
+java.toolchain.languageVersion.set(JavaLanguageVersion.of(21))
+
 android {
     namespace = "saschpe.android.customtabs"
 
@@ -48,13 +50,6 @@ android {
         }
     }
 
-    compileOptions {
-        sourceCompatibility = JavaVersion.VERSION_17
-        targetCompatibility = JavaVersion.VERSION_17
-    }
-
-    kotlinOptions.jvmTarget = "17"
-
     testOptions.unitTests.isIncludeAndroidResources = true
 
     publishing {