Improve CI checks (#12)

Author: PetrHeinz

.github/workflows/java_build.yaml

@@ -8,33 +8,35 @@ on:
       - opened
       - synchronize
       - reopened
+   schedule:
+      - cron: '20 5 * * 1'
+   workflow_dispatch:
+
 jobs:
    build:
       runs-on: ubuntu-latest
+
+      strategy:
+         matrix:
+            java-version: [ 8, 11, 17, 20 ]
+         fail-fast: false
+
       steps:
       -  name: Checkout project
-         uses: actions/checkout@v2
+         uses: actions/checkout@v3
          with:
             fetch-depth: 0
       -  name: Set up JDK
          uses: actions/setup-java@v1
          with:
-            java-version: 8
+            java-version: ${{ matrix.java-version }}
       -  name: Cache Maven packages
          uses: actions/cache@v1
          with:
             path: ~/.m2
-            key: ${{ runner.os }}-m2-${{ hashFiles('**/pom.xml') }}
+            key: ${{ runner.os }}-m2-java${{ matrix.java-version }}-${{ hashFiles('**/pom.xml') }}
             restore-keys: ${{ runner.os }}-m2
-      -  name: Build with Maven on Java 8
-         run: mvn -B clean package --file pom.xml
-         env:
-            BETTER_STACK_SOURCE_TOKEN: ${{ secrets.BETTER_STACK_SOURCE_TOKEN }}
-      -  name: Set up JDK
-         uses: actions/setup-java@v1
-         with:
-            java-version: 11
-      -  name: Build with Maven on Java 8
+      -  name: Build with Maven
          run: mvn -B clean package --file pom.xml
          env:
             BETTER_STACK_SOURCE_TOKEN: ${{ secrets.BETTER_STACK_SOURCE_TOKEN }}