Use the checkout action, version 4. More info in https://github.com/actions/checkout

Author: josealonso

.github/workflows/java.yml

@@ -14,7 +14,11 @@ jobs:
   check-java-exercises:
     runs-on: ubuntu-22.04
     steps:
-      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
+      - name: Checkout the latest commit on the main branch
+        uses: actions/checkout@v4
+        with:
+          ref: main
+
       - uses: actions/wrapper-validation-action@v1
       - uses: actions/setup-java@v3
         with: