krishna Mohan Athota wrote:
An abstract "Inner Class" is also an abstarct element. So i beleive we should modify the class outer also with abstract modifier. why we are not geeting the compilation ERROR?
Inner classes are not like methods, the are classes. When you declare abstract inner class, you can declare its subclasses in the same outer class, and implement different inner class realizations, and use all of them in your outer class as needed. You can even have abstract private inner class, since all it's subclasses can be implemented inside the same outer class.
Remember you cannot have abstract private methods, cause abstract methods are all due to overriding in some descendant classes.