How to use classes from other modules?

Hi everyone,

Is it possible to use other classes from other module in my custom module? In case of page and view, I have to recreate page and view in my custom module so that I can enhance it but how's about classes? It has many dependencies from base classes. Do I need to do the same way as page and view? This way would need a lot of effort. Please share your ideas.

Thanks,

Daro