CareerCup

1)Abstract Class has a constructor. Interface does not have a constructor.
2)Abstract Class can have non-abstract methods. Interface can only have abstract methods.
3)Abstract Class is a good choice when the design does not change or a default behavior is required for some of the methods.
Interface is a good choice when the design changes on a frequent note or no default behavior is required.

One more...
all methods are public in interfaces but abstract classes can have both public and private methods:)

3rd point : is it not opposite ? I mean, when the design does not change you choose Interface ?

3rd Point : As per my understanding, that design change means about the default behavoiur.

variables inside interface are by default final hence needs to be initialized.

one interface can extend many interfaces, but 1 abstract class can extend only 1 other class. so interfaces helps to provide the feature of multiple inheritance

one interface can extend many interfaces, but 1 abstract class can extend only 1 other class. so interfaces helps to provide the feature of multiple inheritance in java.