I wanted to know whether the subclasses of Displayable, Screen and Canvas can be used interchangeably in the same program. It will be easier to write menu's using List and the other game part of the application using Canvas, but I am not sure if we can use both together.
Do you mean using Canvas and Screen in the same MIDlet, or mixing the two in the same display, such as a Form with a paint method? A single MIDlet can mix as many forms and canvasses as it wants, but you cannot mix the two in a single display. (You cannot 'append' a TextField onto a Canvas, for example)