...
import io.appium.java_client.AppiumDriver;
import io.appium.java_client.android.Activity;
import io.appium.java_client.android.AndroidElement;
...

    private static AppiumDriver<AndroidElement> driver;
    private StartsActivity startsActivity;

        ...
        DesiredCapabilities capabilities = new DesiredCapabilities();
        ...
        driver = new AppiumDriver<>(...);

        ...
        startsActivity = new StartsActivity() {
            @Override
            public Response execute(String driverCommand, Map<String, ?> parameters) {
                return driver.execute(driverCommand, parameters);
            }

            @Override
            public Response execute(String driverCommand) {
                return driver.execute(driverCommand);
            }
        };
        Activity activity = new Activity("io.appium.android.apis", ".ApiDemos");
        startsActivity.startActivity(activity);

MobileCommand.commandRepository.put("someCommand", new AppiumCommandInfo("someUrl", HttpMethod.POST));