Sending notification even if there is no update done in the server

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SQL-Server

Android

My problem is that the code should send notification only when i add a new offer by checking in the server every 20seconds where offerNumber > the offer number we already have and when offer number become > offer number that we have, it sends notification with new offer added. But, it sends notification every 20 seconds even if there is no update .. I need to send notification only when offerNumber>offerNum

What I have tried:

public class service extends IntentService {
ResultSet resultSet;
String offerTitle;
public static int offerNum = 0;
String msg="";
ConnectSQL connectSQL = new ConnectSQL();
public static boolean ServiceIsRun = false;

public service() {
    super("MyWebRequestService");
}

@Override
protected void onHandleIntent(@Nullable Intent workintent) {

    while (ServiceIsRun) {
        try {
            resultSet = connectSQL.RunSearch("SELECT * FROM offerdetails where offernumber> " + offerNum + " ", this);

            if (resultSet.next()) {
                msg= resultSet.getString(1).toString();
                offerNum = resultSet.getInt(9);
            }

           Intent intent = new Intent();
            //set the action that will receive our broadcast
            intent.setAction("com.example.Broadcast");
            // add data to the bundle
            intent.putExtra("msg", msg);
            // send the data to broadcast
            sendBroadcast(intent);
        } catch (SQLException e) {
            Toast.makeText(getApplication(), e.getMessage(), Toast.LENGTH_LONG).show();
            e.printStackTrace();
        }
        try {
            Thread.sleep(20000);
        } catch (Exception ex) {
        }
    }
}