This is an anonymous class that extends MyThread and overrides its run() method.
When you start this thread the overriden method is executed and it prints "foo".
This is an anonymous class that extends MyThread and does not override its run() method. The run() method is overloaded instead.
When you start this thread the run() method from MyThread is executed and it prints "Bar".
Look for all places where you create an instance of ClientV1. Make sure you create an instance only once. When you see the second occurrence of new ClientV1 think whether you could use the instance you already have.
I tried running your code and, as I said, pisarz was null.
It was null because you have never called konfigurujKomunikacje on the visible instance of ClientV1.
Note that you are creating two instances. One gets konfigurujKomunikacje called and the other is made visible.
You need to make sure you operate only on a single instance of the client.