An Interfaces defines a public contract of methods for the
classes that implement it. An implementing class must
implement all the method defined by the interface.

An abstract class on the other hand not only defines a
public contract of methods but may also provide partial
implementation of some or all of the class methods. A
subclass of an abstract class inherits the partial
implementation (if any) or must provide a concrete
implementation of the abstract methods.

An abstract class can have concrete method, which is not 
allowed in an interface. Abstract class can have private or 
protected methods and variables and only public methods and 
variables are allowed in interface. We can implement more 
than one interface , but we can extend only one abstract 
class. Interfaces provides loose coupling where as abstract 
class provides tight coupling.

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

abstract is a class and its fulfilling while the subclass 
is extends the abstract class methods.
where as interface also a class it declare a methods.we 
must override all the methods at implements the interface.

abstract class is the one which canhave both abstract as 
well as non abstract methods
Interface is the one which has all the methods are abstract