An example of abstraction in java

[rajaraman navaneethan]

hi friends,
recently in an interview i was asked to explain basic 4 OOPs concepts with examples.i was able to explain inheritance,polymorphism,encapsulation with practical programming examples.

i was not able to give a programming example to illustrate abstraction.can any one of you give an example of a java program which illustrates abstraction?

regards,
Raja

[Keith Pitty]

Any application that defines a Class that is used to instantiate objects is one that demonstrates abstraction.

The analytical process of recognising that several real-world objects share enough characteristics to be considered as members of the same class is abstraction.

[Amit Agrawal]

Originally posted by rajaraman navaneethan:
hi friends,
recently in an interview i was asked to explain basic 4 OOPs concepts with examples.i was able to explain inheritance,polymorphism,encapsulation with practical programming examples.

i was not able to give a programming example to illustrate abstraction.can any one of you give an example of a java program which illustrates abstraction?

regards,
Raja

Threads, IO, Sockets, JDBC....

can you give some examples where you don't see abstraction in Java...

[Sameer Jamal]

A nice example is given here

[rajaraman navaneethan]

hi friends,
thank you all of you for giving the answers.
raja

[rohith das]

here is an example

abstract Abstclass{
int x, y;
...
void method1(int X, int Y) {
...
}
abstract void method2();
abstract void method3();
}


class Subclass1 extends Abstclass {
void method2() {
...
}
void method3() {
...
}
}
class Subclass2 extends Abstclass {
void method2() {
...
}
void method3() {
...
}
}


hope this will help you

[Embla Tingeling]

[

rajaraman navaneethan wrote:i was able to explain inheritance,polymorphism,encapsulation with practical programming examples.

If you explained encapsulation you also explained abstraction. This is because data abstraction is one of the two major aspects of encapsulation (the other is information hiding).

When you encapsulate something you get an outside and an inside. Take any encapsulated unit, like a primitive or an object for example. The way you can use it and how it behaves is the data abstraction. Hidden inside is the implementation.

In Java you usually define your own data abstraction by putting together a set of non-private methods in the form of a class or an interface.

[jaibardhan Ruwari]

Abstraction is only giving essential details w/o any background information.This is achieved in java by
1) Abstract Class and Interface //We don't know the function implementation of code until unless at run time or we have a information about the class which implementing this Interface or Extends this Abstract Class If we click on this method it directly take us to Interface method not to Class which actually implementing this method.
2) Hiding information by access modifier only give access to required
3) Object - Nothing can be access by Object ref.

[Campbell Ritchie]

Welcome to the Ranch

I think this thread would sit better on another forum (not diversions), so I shall move it

[quick nikhil]

One more simple example for abstraction for Beginners:

Abstraction Example:

ClassA.java

abstract class ClassA {
int x, y;
void method1(int X, int Y) 
{}
abstract void method2();
abstract void method3();
}

ClassB.java

public class ClassB extends ClassA{
	void method2() 
	{
		System.out.println("this is Method 2 of class B");
	}
	void method3() 
	{
		System.out.println("this is Method 3 of class B");
	} 
}

ClassC.java

public class ClassC extends ClassA {
	void method2() 
	{
		System.out.println("this is Method 2 of class c");
	}
	void method3() 
	{
		System.out.println("this is Method 3 of class c");
	}
}

MainClass.java

public class MainClass{
	public static void main(String[] args) {
		ClassA obj1= new ClassB();
		obj1.method2();
		obj1.method3();
		ClassA obj2= new ClassC();
		obj2.method2();
		obj2.method3();
	}
}

Out Put:

this is Method 2 of class B
this is Method 3 of class B
this is Method 2 of class c
this is Method 3 of class c

[Campbell Ritchie]

Welcome to the Ranch
Always use the code button; I have edited your post and you can see how much better it looks.
That doesn’t show abstraction at all, I am afraid. It shows abstract classes.

[quick nikhil]

okay..Campbell Ritchie..

I will do the same next time..Thanks a ton..

[dennis deems]

An example from the standard Java libraries is the Calendar class. Calendar is abstract; when you call its getInstance method, you are getting an instance of the concrete implementation (GregorianCalendar, BuddhistCalendar, ...) that is appropriate to your particular Locale.

[Winston Gutkowski]

quick nikhil wrote:One more simple example for abstraction for Beginners:

I hate to say, but I think it would be a lot better if your example had properly named classes, because I'm with Keith: abstraction is
"the analytical process of recognising that several real-world objects share enough characteristics to be considered as members of the same class".
(very nicely put; I'm going to have to remember that one ).

@rajaraman: I guess my question would be: Do you want an example of abstraction, or the use of an abstract class?
Because the two things aren't quite the same.

Winston