Show warning if java code needs formatting

Add a workflow for java formatting

Pull Request resolved: pytorch#4855

.ci/docker/common/install_linter.sh

@@ -13,3 +13,7 @@ source "$(dirname "${BASH_SOURCE[0]}")/utils.sh"
 # NB: Install all linter dependencies, the caching of lintrunner init could be
 # done after Executorch becomes public
 pip_install -r requirements-lintrunner.txt
+
+# Install google-java-format
+curl -L --retry 3 https://github.com/google/google-java-format/releases/download/v1.23.0/google-java-format_linux-x86-64 > /opt/google-java-format
+chmod +x /opt/google-java-format

.github/workflows/lint.yml

@@ -54,3 +54,20 @@ jobs:
           lint.json || true
 
         exit $RC
+
+  android-java-format:
+    uses: pytorch/test-infra/.github/workflows/linux_job.yml@main
+    with:
+      runner: linux.2xlarge
+      docker-image: executorch-ubuntu-22.04-linter
+      fetch-depth: 0
+      ref: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.sha || github.sha }}
+      script: |
+        FILES_NEEDS_FORMAT=$(/opt/google-java-format -n extension/android/src/main/java/org/pytorch/executorch/*.java \
+          examples/demo-apps/android/ExecuTorchDemo/app/src/main/java/com/example/executorchdemo/*.java \
+          examples/demo-apps/android/LlamaDemo/app/src/main/java/com/example/executorchllamademo/*.java)
+        if [ -n "$FILES_NEEDS_FORMAT" ]; then
+          echo "Warning: The following files need formatting. Please use google-java-format."
+          echo "$FILES_NEEDS_FORMAT"
+          exit 1
+        fi