GH-127 - Upgrade CI to Java 9.

Author: odrotbohm

Diff for: .github/workflows/build.yml

@@ -13,13 +13,13 @@ jobs:
 
     steps:
 
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
 
-    - name: Set up JDK 8
-      uses: actions/setup-java@v2
+    - name: Set up JDK 9
+      uses: actions/setup-java@v4
       with:
         distribution: 'temurin'
-        java-version: 8
+        java-version: 9
         cache: 'maven'
 
     - name: Build with Maven