R Systems International Android Developer Interview Questions and Answers

Interface defines only method signatures while abstract class can have both method signatures and implementations.

• An interface can be implemented by multiple classes while a class can only extend one abstract class.

• An abstract class can have constructors while an interface cannot.

• An abstract class can have non-abstract methods while an interface can only have abstract methods.

• An abstract class can have instance variabl...read more

A singleton class is a class that can only have one instance created at a time.

• Singleton classes are often used for managing resources that should only have one instance, such as a database connection or a configuration file.

• They are implemented by making the constructor private and providing a static method to access the single instance.

• Singleton classes can also implement interfaces and inherit from other classes.

• Exa...read more