Abstract Class:

– Every time a concrete subclass is instantiated, the default constructor of abstract classes is called.
– It includes both Non-Abstract and Abstract methods.
– Classes which extend Abstract should not have to implement all methods, only Abstract methods should be implemented in concrete sub-classes.
– Instance variables are present in abstract classes.

Interface:

– No constructor exists for it; hence it cannot be instantiated.
– Only the abstract method should be declared.
– The classes implementing the interface should implement all the methods.
– Only constants are present in the interface.