Use java 21 (#124)

.github/workflows/maven.yml

@@ -17,10 +17,10 @@ jobs:
     steps:
       - name: Checkout this PR planetiler-openmaptiles repo
         uses: actions/checkout@v4
-      - name: Set up JDK 17
+      - name: Set up JDK 21
         uses: actions/setup-java@v3
         with:
-          java-version: 17
+          java-version: 21
           distribution: 'temurin'
           cache: 'maven'
       - name: Ensure code formatted with mvn spotless:apply
@@ -33,12 +33,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ ubuntu-latest, macos-latest, windows-latest ]
-        jdk: [ 17 ]
-        include:
-          - os: ubuntu-latest
-            jdk: 18
-          - os: ubuntu-latest
-            jdk: 19
+        jdk: [ 21 ]
     runs-on: ${{ matrix.os }}
     timeout-minutes: 15
     steps:
@@ -66,10 +61,10 @@ jobs:
     steps:
       - name: Checkout this PR planetiler-openmaptiles repo
         uses: actions/checkout@v4
-      - name: Set up JDK 17
+      - name: Set up JDK 21
         uses: actions/setup-java@v3
         with:
-          java-version: 17
+          java-version: 21
           distribution: 'temurin'
           cache: 'maven'
       - run: ./scripts/regenerate-openmaptiles.sh
@@ -88,7 +83,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v3
         with:
-          java-version: 17
+          java-version: 21
           distribution: 'temurin'
           cache: 'maven'
       - name: Build this branch
@@ -127,7 +122,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v3
         with:
-          java-version: 17
+          java-version: 21
           distribution: 'temurin'
           cache: 'maven'
       - name: Build and test this branch