Use jdk 21

Author: bmalinowsky

.github/workflows/gradle.yml

@@ -13,7 +13,7 @@ jobs:
 
     strategy:
       matrix:
-        java: [17, 21]
+        java: [21]
     name: Java ${{ matrix.java }} sample
 
     steps:

README.md

@@ -4,7 +4,7 @@ Calimero-core [![CI with Gradle](https://github.com/calimero-project/calimero-co
 git clone https://github.com/calimero-project/calimero-core.git
 ~~~
 
-Calimero-core provides (secure) KNX communication protocols, KNX datapoint & property access, and management functionality. [JDK 17](https://openjdk.org/projects/jdk/17/) (_java.base_) is the minimum required runtime environment.
+Calimero-core provides (secure) KNX communication protocols, KNX datapoint & property access, and management functionality. [JDK 21](https://openjdk.org/projects/jdk/21/) (_java.base_) is the minimum required runtime environment.
 Calimero was developed with a focus on applications that run on embedded devices and require a small footprint.
 
 Code examples for using this library are shown in the [introduction](https://github.com/calimero-project/introduction).

build.gradle.kts

@@ -27,7 +27,7 @@ version = "3.0-SNAPSHOT"
 
 java {
 	toolchain {
-		languageVersion.set(JavaLanguageVersion.of(17))
+		languageVersion.set(JavaLanguageVersion.of(21))
 	}
 	withSourcesJar()
 	withJavadocJar()

jitpack.yml

@@ -1,2 +1,2 @@
 jdk:
-  - openjdk17
+  - openjdk21