Android_Service.java

/**
* create service
*/
public class service_Name extends Service {
    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onCreate() {
        super.onCreate();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
		// when service start this method will run
        return START_STICKY;
    }

    @Override
    public void onDestroy() {
        // if we call this method service will destroy
        super.onDestroy ();
    }
}

/**
* call service from activity
*/
startService(new Intent(current_activity_name.this, service_Name.class));

//service_Name, current_activity_name