Weird behaviour on singleton class

Question

I've build a singleton class to check if I am online before performing an external database upload.

To do so, this is the class:

public class InternetConnection
{
    private static InternetConnection instance = null;

    public static InternetConnection getInstance()
    {
        if(instance == null)
        {
            instance = new InternetConnection();
        }

        return instance;
    }


    private InternetConnection()
    {

    }

    public boolean isOnline(Context context)
    {

        ConnectivityManager connMgr = (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
        return (networkInfo != null && networkInfo.isConnected());

    }
}

Outside, on an Activity, I call it like so:

if (InternetConnection.getInstance().isOnline(this)) {
  //I am online, so I upload to my external database
} else {
  // I am not online
}

However, when it enters in getInstance() method, it evaluates instance == null ( which when I debug is true ) but, instead of entering in true branch and performing instance = new InternetConnection() it skips this branck and returns null, which causes a null object exception outside.

Why is this happening? How is possible that if instance == null is true it skips the branch for true case?

Thanks!

It works fine for me, try cleaning and building the project again. let us know if the problem persists after that — SCouto, Jun 08 '16 at 07:23
+1 as everyone has mentioned that it works... if you want to look further http://stackoverflow.com/questions/37397014/implementing-the-singleton-pattern-for-accessing-an-object-anywhere/37398014#37398014 — Pankaj Nimgade, Jun 08 '16 at 07:32
You are right, cleaning project worked! Thank you very much! — Toni, Jun 08 '16 at 07:51
Are you using multithreading? may be you need to use synchronized on getInstance function? — uelordi, Jun 08 '16 at 07:59

Weird behaviour on singleton class

0 Answers0