In abstract class concrete methods are also there. concrete 
methods are the one which has implementation. so in future 
if any programmer wants to give concrete methods can use 
abstract class not interface. 
In abstract class for methods and variables 
public,private,protected modifier can be use. but in 
interface public and abstract are permitted.

if all the methods are abstract in abstract class,then the 
only difference left is,,,,

interface can have static and final variables with public 
and abstract access modifier only ,,,while abstract class 
can have any type of variable with any type of access 
modifiers

Multiple inheritance is possible only through interface,not 
with abstract class. So if u have an interface we can go 
implementing multiple interfaces rather than extending a 
single abstract class.

Methods in the abstract class can be accessed only through 
a class hierarchy i.e through inheritance.

But methods in the interface can be accessed anywhere i.e 
across the class hierarchy.(without inheritance).