Upgrade Java baseline to 24

.github/PULL_REQUEST_TEMPLATE/java24-upgrade.md

@@ -0,0 +1,13 @@
+## Summary
+- Spec issue: #87
+- ADR/design review discussion: https://github.com/ganesh47/java-99-problems/discussions/86
+- Wiki page for spec/ADR: https://github.com/ganesh47/java-99-problems/wiki/Spec-Upgrade-Java-Baseline-to-24
+
+## Required checks
+- [ ] spec-kit templates refreshed (`specs scan --refresh-spec-kit` or `specs templates`)
+- [ ] Spec-kit availability check passed (`npm run spec-kit:check`)
+- [ ] Specs coverage run
+- [ ] Example conformance run (if applicable)
+- [ ] Security scans (Semgrep/OSV-Scanner/Gitleaks/Checkov) green
+- [ ] ADR/design review approved before merge
+- [ ] Issue and project status updated (Todo → In Progress → Done)

.github/workflows/build.yml

@@ -38,6 +38,7 @@ jobs:
       - name: Configure Java-specific args
         run: |
           if [ "${{ matrix.java }}" = "24" ]; then
+            echo "SpotBugs is skipped on Java 24 to keep CI green."
             echo "EXTRA_ARGS=-Dspotbugs.skip=true" >> "$GITHUB_ENV"
           fi
 

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## v0.2.0 - Java 24 baseline
+- Set Java 24 as the default toolchain in Maven and align plugin configs.
+- Document Java 24 usage in README and keep CI green on Java 24.
+
 ## v0.1.0 - Specs bootstrap
 - Add specs scaffolding, Codex wrappers, and guard/coverage/security/release workflows.
 - Add spec-kit template availability check and ADR/wiki automation for specs sync.

README.md

@@ -47,9 +47,10 @@ bash ./mvnw test
 
 1. Clone the repository
 2. Import as a Maven project
-3. Browse the problems in order, starting from P01
-4. Run tests to verify your understanding
-5. Check the test cases for usage examples
+3. Use Java 24 (Temurin 24 recommended)
+4. Browse the problems in order, starting from P01
+5. Run tests to verify your understanding
+6. Check the test cases for usage examples
 
 Each problem's implementation and its corresponding test class can be studied independently, making it easy to focus on specific concepts or challenges.
 

pom.xml

@@ -9,6 +9,9 @@
     <version>1.0-SNAPSHOT</version>
 
     <properties>
+        <java.version>24</java.version>
+        <!-- PMD 3.26.0 does not support targetJdk 24 yet. -->
+        <pmd.targetJdk>23</pmd.targetJdk>
         <maven.compiler.source>${java.version}</maven.compiler.source>
         <maven.compiler.target>${java.version}</maven.compiler.target>
         <maven.compiler.release>${java.version}</maven.compiler.release>
@@ -63,7 +66,7 @@
                 <artifactId>maven-pmd-plugin</artifactId>
                 <version>3.26.0</version>
                 <configuration>
-                    <targetJdk>22</targetJdk>
+                    <targetJdk>${pmd.targetJdk}</targetJdk>
                 </configuration>
                 <executions>
                     <execution>
@@ -93,8 +96,7 @@
                 <artifactId>maven-compiler-plugin</artifactId>
                 <version>3.13.0</version>
                 <configuration>
-                    <source>22</source>
-                    <target>22</target>
+                    <release>${java.version}</release>
                 </configuration>
             </plugin>
 

specs/java-99-java24-upgrade.feature.md

@@ -0,0 +1,38 @@
+---
+spec_id: java24.upgrade
+title: Upgrade Java Baseline to 24
+features:
+  - id: toolchain.java24
+    accept:
+      - "pom.xml defines java.version=24 and compiler config consumes the property"
+      - "PMD targetJdk is pinned to the highest supported level with rationale noted"
+      - "mvnw verify defaults to Java 24 when no -Djava.version override is supplied"
+  - id: ci.java24
+    accept:
+      - "CI builds include Java 24 and pass with -Djava.version=24"
+      - "Java 24-specific skips (if any) are documented and keep checks green"
+  - id: examples.java24
+    accept:
+      - "Problem implementations and tests compile/run under Java 24 in CI"
+  - id: docs.release
+    accept:
+      - "CHANGELOG.md contains a v0.2.0 entry for the Java 24 upgrade"
+      - "Release workflow publishes v0.2.0 with coverage artifact and ADR/wiki links"
+  - id: spec.workflow
+    accept:
+      - "Spec issue/ADR/wiki links created via specs sync and ADR approved before implementation"
+      - "PR uses the spec template with issue/ADR/wiki links and required checks green"
+---
+
+## Summary
+Move the java-99-problems baseline to Java 24 by updating the Maven toolchain defaults and CI expectations. This keeps local builds consistent with CI, and documents the change via changelog and release automation.
+
+## Workflow
+- Todo → In Progress: create spec, sync issue/ADR/wiki, and approve ADR.
+- Implementation: update pom toolchain defaults to Java 24 and align plugin configs; keep CI green.
+- Release: add changelog entry and run release workflow for v0.2.0.
+- Done: sync and close the spec after release and green checks.
+
+## Notes
+- CI already runs Java 24; this spec makes Java 24 the default without overrides.
+- If any plugin requires a temporary Java 24 skip, document it in the workflow.

specs/java-99-java24-upgrade.plan.md

@@ -0,0 +1,39 @@
+# Implementation Plan: java24.upgrade
+
+**Branch**: `java24-upgrade` | **Date**: 2026-01-03 | **Spec**: specs/java-99-java24-upgrade.feature.md  
+**Input**: Spec doc + spec-kit templates (`specs templates` or `specs scan --refresh-spec-kit`)
+
+## Summary
+Set Java 24 as the default toolchain by updating Maven properties and plugin configs, keep CI green on Java 24, document the change in CHANGELOG.md, and ship a v0.2.0 release.
+
+## Technical Context
+**Language/Version**: Java (Maven), target baseline 24  
+**Primary Dependencies**: Maven compiler plugin, PMD, SpotBugs, GitHub Actions  
+**Testing**: Maven CI workflow (build.yml), specs guard/coverage/security  
+**Target Platform**: GitHub repo with Specs Board + release workflow
+
+## Project Structure
+```
+specs/
+├── java-99-java24-upgrade.feature.md
+├── java-99-java24-upgrade.plan.md
+└── java-99-java24-upgrade.tasks.md
+pom.xml
+.github/workflows/build.yml
+CHANGELOG.md
+```
+
+## Implementation Strategy
+1) Create spec + plan/tasks; run `specs sync` to open issue/ADR/wiki.
+2) Approve ADR before implementation.
+3) Update pom defaults: define java.version=24 and align compiler/PMD configs to use it.
+4) Ensure CI expectations for Java 24 remain green; document any 24-specific skips.
+5) Add v0.2.0 entry to CHANGELOG.md and run release workflow with issue/ADR/wiki links.
+6) Run `specs sync` and `specs close` after release and green checks.
+
+## Dependencies & Execution Order
+- ADR approval before implementation.
+- Release requires CHANGELOG.md entry for v0.2.0.
+
+## Notes
+- Use the spec-specific PR template with issue/ADR/wiki links.

specs/java-99-java24-upgrade.tasks.md

@@ -0,0 +1,24 @@
+# Tasks: java24.upgrade
+
+**Input**: spec (`specs/java-99-java24-upgrade.feature.md`), plan (`specs/java-99-java24-upgrade.plan.md`), spec-kit templates  
+**Prerequisites**: ADR approved; templates refreshed
+
+## Format: `[ID] [P?] [Story] Description`
+
+## Phase 1: Spec setup
+- [ ] T001 [P] [SPEC] Create spec, plan, and tasks files.
+- [ ] T002 [P] [SPEC] Run `specs sync` to create issue/ADR/wiki links.
+- [ ] T003 [P] [SPEC] Approve ADR and update with plan/tasks.
+
+## Phase 2: Java 24 baseline
+- [ ] T010 [P] [BUILD] Define java.version=24 and align compiler/PMD configs.
+- [ ] T011 [P] [BUILD] Confirm CI Java 24 checks remain green; document any 24-specific skips.
+- [ ] T012 [P] [BUILD] Add spec-specific PR template with issue/ADR/wiki links.
+
+## Phase 3: Release + close
+- [ ] T020 [P] [REL] Add v0.2.0 entry to CHANGELOG.md.
+- [ ] T021 [P] [REL] Run release workflow for v0.2.0 (issue/ADR/wiki inputs).
+- [ ] T022 [P] [REL] Run `specs close java24.upgrade --issue <#> --pr <#>` after release + green checks.
+
+## Dependencies & Execution Order
+- Phase 1 → Phase 2 → Phase 3.