Answer / amit patel

Abstract class is used to implement common behavior which is
required by all subclasses but have some behavior which is
specific to subclass.

E.g., you want to implement a DocumentViewer App. Basic
operations are like open, view and close. open and close
requires no specific implementation while view require
specific implementation. Make DocumentViewer abstract,
implement open, close and make view as abstract. Now view is
responsibility of subclass. Like PDFViewer will have own
implementation for view()

Answer / rakesh@crr

if a class contains abstract method,that class must be
declared as a abstract class. abstract methods contains only
declarations. it does not contain objects.

Answer / surendra

Abstract classes are use to give functionality to the users.
The functionality is given by the class, use use this
functionality as per his/her requirements. Abstract classes
gives additional functionality to put one or two methods
common for each user and may put others abstract to fullfill
users requirements.

Answer / sumanth gatla

there is no rule that an abstract class must contain one
abstract method. with out single abstract method also
abstract class exist
eg........HTTPServlet

Answer / vishu

abstract class caontains only abstract mehtods all methods
that have to define before they are decalring in the next
class

& we dosn't create object of the abstract class

Answer / harshavardhan

In Inheritance , class become more general and more
abstract.Ancestor classes are more general, i.e more basis
for other classes.Abstract classes can have fields and
concrete methods.Methods are declared not defined so we can
not create objects. but we can create object variables of an
abstract class. but such variable must refer to an object of
a nonabstract subclass.

Answer / venkatesh

abstract class have atleast abstract method
it is maily used for to prevent create object of class.

Is this valid in java ? Can we instantiate interface in java?

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