Support building with JDK 21 (#234)

- Update google-java-format to a version compatible with JDK 21 and run "gw spotlessApply".
- Fix wrong test assumption
  JavaCodeGenerator writes a properties file using java.util.Properties,
  which doesn't guarantee order of entries.
- Fix most deprecation warnings
- Add CI job for JDK 21

.circleci/config.pkl

@@ -148,6 +148,10 @@ local gradleCheckJobs: Mapping<String, GradleCheckJob> = new {
     javaVersion = "17.0"
     isRelease = false
   }
+  ["gradle-check-jdk21"] {
+    javaVersion = "21.0"
+    isRelease = false
+  }
 }
 
 jobs {

.circleci/config.yml

@@ -615,6 +615,24 @@ jobs:
       LANG: en_US.UTF-8
     docker:
     - image: cimg/openjdk:17.0
+  gradle-check-jdk21:
+    steps:
+    - checkout
+    - run:
+        command: ./gradlew --info --stacktrace check
+        name: gradle check
+    - run:
+        command: |-
+          mkdir ~/test-results/
+          find . -type f -regex ".*/build/test-results/.*xml" -exec cp {} ~/test-results/ \;
+        name: Gather test results
+        when: always
+    - store_test_results:
+        path: ~/test-results
+    environment:
+      LANG: en_US.UTF-8
+    docker:
+    - image: cimg/openjdk:21.0
   bench:
     steps:
     - checkout
@@ -765,6 +783,9 @@ workflows:
     - gradle-check-jdk17:
         requires:
         - hold
+    - gradle-check-jdk21:
+        requires:
+        - hold
     - check-patch-file:
         requires:
         - hold
@@ -776,6 +797,7 @@ workflows:
     jobs:
     - gradle-check-jdk11
     - gradle-check-jdk17
+    - gradle-check-jdk21
     - check-patch-file
     - bench
     - gradle-compatibility
@@ -788,6 +810,7 @@ workflows:
         requires:
         - gradle-check-jdk11
         - gradle-check-jdk17
+        - gradle-check-jdk21
         - check-patch-file
         - bench
         - gradle-compatibility
@@ -820,6 +843,12 @@ workflows:
             ignore: /.*/
           tags:
             only: /^v?\d+\.\d+\.\d+$/
+    - gradle-check-jdk21:
+        filters:
+          branches:
+            ignore: /.*/
+          tags:
+            only: /^v?\d+\.\d+\.\d+$/
     - check-patch-file:
         filters:
           branches:
@@ -872,6 +901,7 @@ workflows:
         requires:
         - gradle-check-jdk11
         - gradle-check-jdk17
+        - gradle-check-jdk21
         - check-patch-file
         - bench
         - gradle-compatibility
@@ -917,6 +947,9 @@ workflows:
     - gradle-check-jdk17:
         requires:
         - hold
+    - gradle-check-jdk21:
+        requires:
+        - hold
     - check-patch-file:
         requires:
         - hold

.circleci/jobs/GradleCheckJob.pkl

@@ -17,7 +17,7 @@ extends "GradleJob.pkl"
 
 import "package://pkg.pkl-lang.org/pkl-pantry/com.circleci.v2@1.1.0#/Config.pkl"
 
-javaVersion: "11.0"|"17.0"
+javaVersion: "11.0"|"17.0"|"21.0"
 
 steps {
   new Config.RunStep {