To create a window, which of thefollowing classes has to be extended?

J frame class has to be extended for the creation of a window

Explanation:

J frame needs to be extended to create a window, this is because this class in windows has a title, support buttons components, a border or we can say it has decorations for windows.  

The rest of the classes like J button and J text fields lie within the J frame and the Container class is a super class and provides only outlines to J Frame class.