You need sometimes to know which screens are in the screens stack of your Blackberry application maybe because you want to remove all the screen below a specific screen because they are not needed anymore.
First of all you can get the active screen using the instruction:
UiApplication.getUiApplication.getActiveScreen();
Once you have the screen object you can call on it the method:
getScreenBelow()
you will get the screen object below. Generally you can move along the stack using also the method
getScreenAbove()
used together with the previous getScreenBelow method.