add distribution to actions/setup-java@2.
diff --git a/.github/workflows/maven.yml b/.github/workflows/maven.yml
index aac9b3b..4d783cd 100644
--- a/.github/workflows/maven.yml
+++ b/.github/workflows/maven.yml
@@ -72,6 +72,7 @@
       - name: Set up JDK
         uses: actions/setup-java@v2
         with:
+          distribution: 'adopt'
           java-version: ${{ matrix.java }}
 
       - name: Build with Maven