abstract

[b reddy]

how do we access a concrete method of an abstract class from a concrete class?

[Keith Lynn]

Could you be more specific?

What relationship does the concrete class have to the abstract class?

[b reddy]

suppose if there is an abstract class x. show() is a concrete method in x class.
y is a class which extends x.
how do we access show() of class x?
can we override methods that are in abstract classes?

[Keith Lynn]

Yes you can override methods that are inherited from abstract classes as long as you obey the usual rules of overriding.

[Bear Bibeault]

"breddy",

There aren't many rules that you need to worry about here on the Ranch, but one that we take very seriously regards the use of proper names. Please take a look at the JavaRanch Naming Policy and adjust your display name to match it.

In particular, your display name must be a first and a last name separated by a space character, and must not be obviously fictitious.

Thanks!
bear
JavaRanch Sheriff

[b reddy]

can we create an object to an abstract class?

[Keith Lynn]

No, you can't create an instance of an abstract class with a constructor.

[Meena R. Krishnan]

Here is an eg. showing how to access / override / overload a concrete method that is declared in the abstract base class.

abstract class absSuper{
void show(){
System.out.println("From super ");

};
}
public class AbstractTest extends absSuper{
void show(){
System.out.println("From AbstractTest - I am overridden");

};

void show(int i ){
System.out.println("From AbstractTest: I'm overloaded");
}
void superShow(){
super.show();
}

public static void main(String... args){
AbstractTest a = new AbstractTest();
a.show();
a.show(8);
a.superShow();
}
 
}

[b reddy]

Hi Keith,
can you tell me the difference between instance variable and an reference variable?

[b reddy]

Hi krishnan,

are you sure that a.supershow() will work?
i dont think so this will work.

[Meena R. Krishnan]

are you sure that a.supershow() will work?
i dont think so this will work.

why do you think so?

superShow() is a method in the extended class which in turn calls the super class' concrete method.

Here is the o/p from the above code.

From AbstractTest - I am overridden
From AbstractTest: I'm overloaded
From super