Try to set JAVA_VERSION env variable

Author: oliemansm

.github/workflows/gradle.yml

@@ -32,9 +32,9 @@ jobs:
           path: |
             ~/.gradle/caches
             ~/.gradle/wrapper
-          key: ${{ runner.os }}-$JAVA_VERSION-gradle-${{ hashFiles('**/*.gradle*') }}
+          key: ${{ runner.os }}-${{ JAVA_VERSION }}-gradle-${{ hashFiles('**/*.gradle*') }}
           restore-keys: |
-            ${{ runner.os }}-$JAVA_VERSION-gradle-
+            ${{ runner.os }}-${{ JAVA_VERSION }}-gradle-
       - name: Make gradlew executable (non-Windows only)
         if: matrix.os != 'windows-latest'
         run: chmod +x ./gradlew