difference between abstractclass and interface
1)Interfaces provide a form of multiple inheritance. A class can extend only one other class.
2)Interfaces are limited to public methods and constants with no implementation. Abstract classes can have a partial implementation, protected parts, static methods, etc.
3)A Class may implement several interfaces. But in case of abstract class, a class may extend only one abstract class.
4)Interfaces are slow as it requires extra indirection to to find corresponding method in in the actual class. Abstract classes are fast.