When you refer to "real time", are you actually meaning in real world example?
Interface is used when you want to define a contract and you don't know anything about implementation.
Abstract class is used when you know something and rely on others for what you don't know.
we want to start a service like "makemytrip.com" or "paytm" where we are responsible for displaying the flights from various flight service company and place an order from customer.
Lets keep our service as simple as,
1.Displaying flights available from vendors like "airasia", "jetair" and "emirates".
2.Place and order for seat to respective vendor.
suppose I have to use few methods everytime like Flight,Flight_time etc i.e complasary to override those methods .so these all are abstract method and service,food that is not complasary that would be considered as non-abstract method.That time using abstract class is not required . because all flight depends on factors like time,service etc..That time interface are not used.