Oh yeah, my fault. It's about line 24, and the full text of error is:
error: cannot find symbol
symbol: variable przycisk
location: class ProstyGUI1
Also, I've compared example from Head First. Java. and my own code. And there's the diffrence:
In my code:
And in the example:
So does the way I will make JButton przycisk (as a component of class or as variable in method). It's all about the diffrence between local and global?