There are 3 repositories under arcgis-maps-sdk-for-java topic.
ArcGIS Maps SDK for Java samples
Starter project for the ArcGIS Maps SDK for Java with Maven
Starter project for the ArcGIS Maps SDK for Java with Gradle
Starter project for the ArcGIS Maps SDK for Java with the SDK zip
ArcGIS Maps SDK for Java code demos
Gradle Plugin for ArcGIS Maps SDK for Java