Question Regarding the Inheritance

[sakthi moorthy]

Hi folks,

I have came across this question in an Interview and not able to answer, The Question is
I have a class A which has one() and two() methods, and I have two another classes B and C both extends A.
The Question is
For class B method one() should be accessible and two() should not be accessible
For class C method one() should not be accessible and two() should be accessible.

use access specifiers, put B and C in another package and so on... But the above condition should meet.

I have tried so many things not able to solve this,

Just wanted to know is it possible ?

[saloni jhanwar]

package pkg1;
public class A{
     protected void one(){};
     void two(){}
}

package pkg2;
import pkg1.a; 
class B extends A{
     void two(){};
}
class C extends B{}

If someone ask illogical question then you can reply answer in same way. .Condition satisfied.

[sakthi moorthy]

Hi Saloni,

I Really Appreciate the way you are thinking , Just wanted to confirm few things with you the method two() in class A is package or default specifier that means class on Another package cant override it, here comes an error

package pkg2;  
import pkg1.a;   
class B extends A {
	@Override
	void two() { // compile time error
	}
}

class C extends B {
}

let me also try parallel, any new ideas are always welcome.

Regards
S.Sathiya

[saloni jhanwar]

Use private access modifier while you define two() in class A.It is working.cheers

[sakthi moorthy]

saloni jhanwar wrote:Use private access modifier while you define two() in class A.It is working.cheers

if you use private access modifier while you define two() in class A, will it satisfy the following statement ?
For class C method one() should not be accessible and two() should be accessible.

BTW I just got the answer that may be one of the way, just wanted to know different ways of thinking and innovative idea's from other people

Hint is I have not used final, static,protected keywords as a access specifiers for the methods. let me post the answer soon.

[saloni jhanwar]

sakthi moorthy wrote:
BTW I just got the answer

I don't need magnifier.I can read.

sakthi moorthy wrote:
if you use private access modifier while you define two() in class A, will it satisfy the following statement ?
For class C method one() should not be accessible and two() should be accessible.

why you have any doubt?? class B and C should extends class A which is going here this condition satisfied and class C has method two you can check.Does this question state specifically that method two should be of class A ??? i think No.

and if you got answer then cheers happy ranching

[sakthi moorthy]

saloni jahnwar wrote:
why you have any doubt?? class B and C should extends class A which is going here this condition satisfied and class C has method two you can check.Does this question state specifically that method two should be of class A ??? i think No.

I think this is your consolidated answer and you are not going to edit it again

ok I will put my question in another way

 // you can place it any packages i.e., same Package or difference Package
             class A {
 
                 <access specifier> void one() { }
                 <access specifier> void two() { }
                      }
  
   

             // you can place it any packages i.e., same Package or difference Package
           class B extends A {
                 @Override 
                 void one() {

                   }

                   @Override
                  [b]void two() { // compile time error[/b]


                   }
                }

    

 // you can place it any packages i.e., same Package or difference Package
           class C extends <A/B> {
                 @Override 
                [b] void one() { // compile time error
[/b]
                   }

                   @Override
                  void two() { 


                   }
                }

    

Note in class B two() method is giving compilation error and class C one() method is giving compilation error

magnifier rules apply

[saloni jhanwar]

Did i override anything in my example??? this above is your code, you wrote this.Why are you asking to me about this ? you should ask to yourself that why you wrote crazy code what craziest thing you wrote above,i think you need much large magnifiers seriously,overriding depends on which access modifier you are using ok.cheers

Now see what i wrote and compare it with above your code

//A.java 
package pkg1;
public class A{  
     protected void one(){System.out.println("class A(one)");};  
     private void two(){System.out.println("class A(two)");}  
} 

//C.java
import pkg1.*;   

class B extends A{  
     void two(){            //it is new method not overriding okay ??
		 System.out.println("class B(two)");
	 };  
}  
class C extends B{
	public static void main(String args[]){
	C c=new C();
	//c.one(); but it fails here
    c.two(); 
	}
} 

[chain singh]

Try this,,,,,,,,

[code=java]

class A
{
public void one() throws NullPointerException{ }
public void two() throws NullPointerException{ }
}

class B extends A
{
public void one() { }


public void two() throws Exception{} // compile time error

}

class C extends A
{

public void one() throws Exception {} // compile time error

public void two() {}
}





[/code]

[sakthi moorthy]

Ease up saloni jhanwar

For class B method one() should be accessible and two() should not be accessible
here accessible means i want to access the method one() of class A,So in class B if you override that method(one()) or

access that method(one()) on another method like following

class B extends A{

public void demo() {
   one();
}

}

 here you will be come to know that method(one()) accessible or not 

For class C method one() should not be accessible and two() should be accessible.
above mentioned same is applicable for this statement also, but vise versa.

what craziest thing you wrote above

yeah i used to write craziest thing, because mistakes only makes us to learn perfect things

Thanks for the answers



chain singh

[saloni jhanwar]

sakthi moorthy wrote:
BTW I just got the answer that may be one of the way, just wanted to know different ways of thinking and innovative idea's from other people
Hint is I have not used final, static,protected keywords as a access specifiers for the methods. let me post the answer soon.

Ok sorry,Now its time to post your answer which you got but did not post until now.I am eager to know how you did without final,static,protected keywords

[sakthi moorthy]

I am eager to know how you did without final,static,protected keywords

Still there is a draw back in my approach, anyhow i will share how i tried to solve this problem


I have made the class A as abstract and method one() as abstract.

       package pck1;
         abstract class A {

             abstract public void one();

             void two() {     }

           } 
 
    

     package pck2;
     class B extends A {

      public void one() {   // method one() defined in class A is accessible

           }

         // you can't access the method two() as class B is in different package 
      }

    // so "For class B method one() should be accessible and two() should not be accessible " statement statified
 

     

   package pck1; // same package as Class A
   abstract C extends A {

        public void demo(){
         two();   // you can access the method two(); because its in same package;
         }
          // here is the drawback of my approach if you override the method one() it will work fine, else if you try to access the method it can't and won't work because its an abstract method


      }
//For class C method one() should not be accessible and two() should be accessible, will be true unless you override method one(); if you override it will be false