👷 Matrix build for multiple jdk versions

Author: langecode

.github/workflows/ci.yaml

@@ -7,12 +7,16 @@ jobs:
   build:
     runs-on: ubuntu-latest
 
+    strategy:
+      matrix:
+        java: [ 8, 12, 15 ]
+
     steps:
       - uses: actions/checkout@v2
       - name: Set up JDK
         uses: actions/setup-java@v1
         with:
-          java-version: 1.8
+          java-version: ${{ matrix.java }}
       - name: Cache Maven packages
         uses: actions/cache@v2
         with: