abstraction in java data abstraction in java abstraction in java with example abstraction example in java
encapsulation vs abstraction in java define abstraction in java example of abstraction in java example for abstraction in java abstraction definition in java definition of abstraction in java abstraction vs encapsulation in java data abstraction in java with example abstraction in java definition abstraction in java with example code abstraction in java in deatil abstraction in java meaning explain abstraction in java
Abstraction :
Abstraction
is one of the distinct feature in Java or Object oriented programming
is a way
to segregate or isolate the implementation from interface. Abstraction is one
of the fundamental principles along with Encapsulation, Inheritance,
Polymorphism,
Class and Object.
Abstraction in
Java can be achieved by using interface and abstract class in Java.
An
interface or abstract class is something which is not implemented or concrete,
something which is incomplete. In order to use interface or abstract class we
need to
implement abstract method into a class by extend and implement abstract
class, interface
with or implement or concrete behavior.
For example regarding Abstraction is creating
interface to denote common features or
behavior without specifying any details
about how that behavior works e.g. You create an
interface called Servlet which
has start() , service() and stop() methods. Service() method
is used for
business logic it is implemented in user defined class. This is called
abstraction
of Servlet because every servlet.
Definition of
Abstraction:
Abstraction is only
providing essential data with respect to any background information.
This is
achieved in java by
1) Abstract
Class and Interface: We are not know about the function
implementation of
code until unless at run time.
we have the
information about the concrete class which implements Interface or Extends
Abstract Class If we go for a particular method it directly take us to
Interface method not to
Class which actually implementing this method.
2) Hiding data by access modifier only gives access that are required.
3) Object - Nothing can be access by Object ref.
What is abstract class in Java
An abstract
class is something which is incomplete and you cannot create instance
of
abstract class. If you want to use it you need to make it complete or concrete
by
extending it. A class is called concrete if it does not contain any abstract
method and
implements all abstract method inherited from abstract class or
interface it has
implemented or extended. By the way Java has concept of
abstract classes, abstract
method but a variable cannot be abstract in Java.
Or
In General
abstract class is a combination of abstract methods and concrete methods.
But
we can create instance for abstract class.
In real time in JDK we are applying abstraction in most of
the cases. For example for
abstract class in Java is ActionListener which has
abstract method called
actionPerformed(ActionEvent ae). This method is called
when an ActionEvent is fired like
when you click on JButton. Its common in java
to attach ActionListener with JButton by
implementing abstract method
actionPerformed(ActionEvent ae) using Anonymous class, as
shown in below
Example :
The Following Code will clarifies how abstract class and
abstract methods are in
usage.
JButton ok = new
JButton("OK");
ok.addActionListener(new ActionListener(){
public
void actionPerformed(ActionEvent ae){
//code
to handle event
}
}
What is Interface in
java ?
In Java
Interface is an another way of providing abstraction, Interfaces are by default
abstract and only contains public static, final constant or abstract methods.
Point To Remember
Regarding Abstraction In Interview View:
About abstraction
in two ways we can provide abstraction one is abstract class and
another way is
through Interface. But It’s very common interview question is that where
should
we use abstract class and where should we use Java Interfaces ?
In my view it is
very important to understand to design better Java application for java.
1) If you can go for java interface if you only know
the name of methods your class
should have e.g. for Server it should have
start() and stop() method but we don't know how
exactly these start and stop
method will work.
2) if you know some of the behavior while designing
class and that would remain common across all subclasses add that into abstract
class. Interface like Runnable are good example of abstraction in Java which is
used to abstract task executed by multiple thread.
1) Use abstraction if you know something needs to be in
class but implementation of that
varies.
2) In Java you cannot create instance of abstract class, its
compiler error.
3) Abstract is a keyword in java.
4) A class automatically becomes abstract class when any of
its method declared as
abstract.
5) abstract method doesn't have method body.
6) variable can not be made abstract , its only behavior or
methods which would be
abstract.
7) If a class extends an abstract class or interface it has
to provide implementation to all
its abstract method to be a concrete class.
alternatively this class can also be abstract.
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