Retrofit set up

ApiCalls.java

public class ApiCalls
{
    public static Call<DummyObject> getDummyObjectCall()
    {
        return ApiServices
                .getDummyService()
                .getDummyObject();
    }

    public static Call<List<DummyObject>> getDummyObjectListCall()
    {
        return ApiServices
                .getDummyService()
                .getDummyObjectList();
    }
}

ApiClients.java

public class ApiClients
{
    private static Retrofit mClient;

    public static Retrofit getApiClient()
    {
        if (mClient == null)
        {
            mClient = new Retrofit
                    .Builder()
                    .baseUrl(BuildConfig.apiDomainName)
                    .addConverterFactory(MoshiConverterFactory.create())
                    .build();
        }

        return mClient;
    }
}

ApiServices.java

public class ApiServices
{
    private static DummyService mDummyService;

    public interface DummyService
    {
        @GET("/v2/55973508b0e9e4a71a02f05f")
        Call<DummyObject> getDummyObject();

        @GET ("/v2/5597d86a6344715505576725")
        Call<List<DummyObject>> getDummyObjectList();
    }

    public static DummyService getDummyService()
    {
        if (mDummyService == null)
        {
            mDummyService = ApiClients
                    .getApiClient()
                    .create(DummyService.class);
        }

        return mDummyService;
    }
}