When i change it to Klasa5 (6, 7, 8, 9 or 0) its OK, but not for (Klasa1, Klasa2, Klasa3 and Klasa4 - gives different error)
Unfortunately (for me) i 've checked it on two other machines and it runs fine with all names.
What kind of magic may be lurking in my JVM that stops me from running this code?
The most likely explanation is that your first machine is already littered with class files named "Klasa1", "Klasa2", etc, somewhere on your class path, and those classes don't include the same constructor. Use your operating system's facilities for finding files to find all files named "Klasa*.class", and delete them, then try again.
Ernest, you were right. I had Klasa1, Klasa2, Klasa3 and Klasa4 class files addressed somwhere in the middle of my CLASSPATH var.
I thought my JVM went crazy, but that was only me in the end ..