The Google Maps repo on GitHub includes a number of samples illustrating the use of the Google Maps Android API in your Android app. In addition, you can find code snippets on each page of this developer's guide.
Sample map activities on GitHub
The ApiDemos repo on GitHub contains a sample app, including a number of activities that illustrate common usages of the API. You can import and build the app, view the demo and use the sample code supplied as a starting-point for your app.
When you run the sample app, it displays a list of available demos that you can run on your own device. Select one of the options. For example, click Basic Map.
Troubleshooting: If the sample app runs successfully but you don’t see a map, check that you’ve added your API key to the app's manifest file, as described in the signup guide.
Sample app for maps on Android Wear
A sample app is available on GitHub, which you can use as a starting point when building a wearable app. The sample shows you how to set up a basic Google Map on Android Wear.