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The constructors could be passed args they could use to make unique contents for their windows. Or there could be unique classes for each window. Its up to the programmer.

Define new classes as needed, not just to have more classes.

Window is the name of a Java SE class. It will be better if you use a unique name vs one used by Java.





public static...

Each instance of the class extending JFrame would have its own window.
Create a class that extends JFrame, create multiple instances of that class and set them all visible.
Something like this:...