Using Zulu builds of OpenJDK in GH actions

The AdoptOpenJDK has been discontinued Since July 2021. When using Zulu you get all the latest updated builds for all versions of OpenJDK. Also, I've added a matrix to later add JDK 17 (next LTS release). Gradle doesn't support JDK early access releases. When using Maven you could add 17-ea.

Author: carldea

.github/workflows/checkstyle.yml

@@ -4,14 +4,17 @@ on: [pull_request]
 jobs:
   build:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        java-version: [ 11 ]
     steps:
       - uses: actions/checkout@v2
 
-      - name: Set up JDK 11
+      - name: Set up JDK ${{ matrix.java-version }}
         uses: actions/setup-java@v2
         with:
-          java-version: '11'
-          distribution: 'adopt'
+          java-version: ${{ matrix.java-version }}
+          distribution: 'zulu'
 
       - name: Check style and license headers
         run: |